My summary of why assassins are in their current spot based on my personal ideas. Kinda long
I would like to start off by saying I'm not claiming that everything I'm about to type out is 100% correct. This entire post will be based on my own theory created from my knowledge, experience, stats from secondary sites, and the general opinion of other players to confirm what I think is right. I may get only a few points correct, I may get it all correct, and then I may be completely wrong on every point.
There is a Summary at the very bottom but one thing you should read out of all of the text below is alittle farther down Marked with a Bold "THIS". It's my own personal idea to the reason behind the assassin update in the first place and might help explain what's in the summary abit better.
From my point of view it started when Riot started drastically changing the state of the game from right about mid to late season 4 onwards. At this point the game had aged and Riot wanted to start updating the game accordingly by implementing drastic changes that'd slowly but surely rework the very foundation the game had built. Everything from classes of items and champions, to game mechanics, and masteries were on the to do list.
It was at this point that the game was still in its golden age where every champion class was more defined. thus each class had its proper place.
Tanks were mainly big bulky utility platforms that didn't do much else.
Dive fighters lacked good utility but dealt moderate damage which was good enough to typically get to the backline to divert attention or assist assassins.
Fighters were a mixture between damage, utility, and in some cases durability but were made to be all rounders so didn't always excel in 1 particular area.
Mages were specialized in applying medium sized amounts of magic damage in large areas to control teamfights.
Assassins always dealt the most amount of damage (atleast in bursts) but specialized in diving and applying it in single target bursts so they were focused on countering ADC's and mages.
ADC's have always focused on DPS so they haven't changed much.
Supports have always been focused on team utility and sometimes being off tanks so they also haven't changed much role wise.
#THIS Assassins at this time were very meta because they were always relevant in the game. There would always be mages in the mid lane and ADC's in the bot lane so naturally, assassins dealing the most damage and specializing in killing those champion classes, they'd always find success as long as the player met the skill requirements to effectively play at their ELO.
Unfortunately, this obviously meant that mages and ADC's would always get hunted down. It didn't make the assassins unbalanced as they were specifically designed to do it and could be dealt with if you were skilled at playing Mages and ADC's. But, for those who weren't, assassins were prone to heavy snowballing thus winning games and creating a frustrating experience for those on the receiving end. This led to the assassin update to give the champion class "Outplay potential" and "Make it fun for both sides".
#Note: From this point on it's simply a recap of patches that I believe lead up to this meta. Just skip to where it says HERE if you don't want to read it. I just kept reading and typing as I went along without thinking about if the information was going to be relevant or add to the point I'm trying to make.
Back to the timeline of things. It was during mid season 4 (maybe even alittle earlier) that riot decided to get started on the first on their to do list: tanks. During season 4 the changes to tanks weren't very large but instead incrementally increased the effectiveness of tanks by small amounts. From reducing the total cost of tank items, to buffing stats on tank items, to sometimes several tank champions getting direct buffs per patch.
What helped to further this was also the mastery tree at the time for defense which was considerably, well, tanky? Unlike the current "Resolve" tree, the old defense tree was mainly focused on actual tank stats. However, another thing that was unlike the current mastery tree, the old mastery trees were filled with ALOT less interactive passives and major changes that'd be noticeably impactful. Instead it was primarily filled with flat and percentage stat increases that'd give minor impact on gameplay by themselves (or atleast most didn't give major impact) but stack up to equal out to a large difference when combined as a whole. The defense tree was I think the biggest culprit of this, filled with a MASSIVE amount of flat and percentage damage reducation, resistances, regeneration, and even a couple of tenacity type masteries. Disclaimer: I'll try to space everything out as cleanly as possible but things might get ugly depending on how long I want to type for.
This is kinda the starting point where riot would create the tank meta and ironically, but not surprisingly, progress into the damage meta that we're currently in.
At this point I believe the tank meta had already been a problem as damage tanks who were previously useless, were just too tanky to kill. They didn't do obscene amounts of damage but were extremely difficult to put down thus, if measures weren't taken they'd eventually kill someone. From what I can learn the main culprits of this were infact Shyvana and Mundo.
Fast forward through season 4 and the start of season 5 and tanks/bruisers have slowly been getting buffs increasing their utility, damage, and also various other changes outside of stat increases to make the champions better. 5 patches into season 5 and we hit a turning point. The introduction of Cinderhulk. Various items had already been buffed, added or reworked around this time including items like ZZ Portal and Righteous Glory, but this was one of the biggest changes which led to the tank jungler meta.
Now for the next very long line of patches we can see these things happening:
ADC's are getting buffs so that teams can rely on their DPS trains to reliably dent the tanks ruling the meta at the time.
AP junglers are getting attention as this was also the time where the magus enchantment was what they were left with. So every AP jungler was in a pretty tough spot at the time.
All sorts of AP mages were getting small tweakers here and there as this was still before the mage rework so the mage role was very stale, lacked variety, and mages were still getting hunted by assassins along with tanks.
An irelia nerf.
The addition of the current black cleaver as a "tank killer" that would late turn into a staple item for all sorts of AD champions. This was also along with a buff to Blade of the Ruined king which shows that they were looking to get options in to kill tanks.
The addition of cinderhulk leading to a one sided slaughter of champions who were abusers of it.
And finally tweaks, buffs, and even a few nerfs to tank champions outside of the jungler/cinderhulk pool.
Now we've gotten to this point. They've realised that they've created literal monsters so they're willing to arm up other champions with whatever is necessary to kill off tanks. Cinderhulk will rest atop it's flaming pedestal untouched till a whole 4 patches after 5.5 where it finally receives its first major nerf with the only other nerf before this being -50 health but also a cost reduction of -50 gold. Unfortunately it got hit but not hard enough. They reduced the damage it dealt but then gave it its trademark increase damage against jungle camps so that Cinderhulk users still kept with the clear speed.
Now in patch 5.12 Riot decides to hit the tanks at their source and go for the masteries. Nerfs were handed out, a few got buffed, but the main thing was that alot of the positions on the mastery tree were swapped so that more points would have to be put into the tree before champions got access to the really good ones.
For the next 4 Patches things remain completely away from tanks as it's the start of the sated devourer and runeglaive meta's so tanks are still there doing roughly the same thing but are definitely not in the spotlight. However at patch 5.16 the real beginning hits: The juggernaut update, AKA the start of tanky damage. The primary things to note here is the introduction of Steraks Gage, Ttitanic Hydra, and Deadmans plate in this patch. The items that've been the biggest problems so far with various champions using these items to become tankier while not sacrificing massive amounts of damage in return.
Things stayed quiet until the Marksman update. This is the rework of the mastery system along with the changes to Iceborn and Triforce, stat increases (not buffs because they're offset by cost increases) to Titanic and Blackcleaver, finally the addition of Phantom dancer and Deaths dance which have also proven to be pretty tanky items on various champions. With the rework of the mastery system in, the power creep hit like a truck. There's mastery upon mastery of free damage increases with the addition of keystones which offered champions unbelievable amounts of free damage. Champions that dealt little damage suddenly dealt a decent amount. Champions that dealt alot suddenly dealt insane amounts of damage.
#HERE
The primary point of this is that the tank meta forced changes that ended with damage items that were solidly tanky. Between tanky damage items and masteries,AD champions of all sorts could access these items without loss or drawbacks to deal more than enough damage to be effective, and it got worse with champions like Hecarim, Lee Sin, and Vi who are capable of building even more defensive stats than other champions who can also build tanky damage. Assassins (Specifically AD assassins) Are simply not capable of utilizing such things as their kits simply aren't designed for it and their stats are considerably lower as well. Both in terms of facing off against each other and in comparison Assassins can't compete with these champions that can rival and easily beat their potential damage as well as typically do the assassins job better while remaining overwhelmingly more durable.
Next is the mages.
Assassins were always around in the first place as a Mage hunter, ADC hunter and in general focused on single target burst and diving. As i said before, while not unbalanced, the typically pattern of assassins stomping mages in the mid lane like they were designed to became a frustrating experience for mages and subsequently, ADC's.
Mages were already being looked at throughout that timeline I listed above because for the longest time each mage felt too similar, the builds were almost all the same, and the role was simply stale and lacked variety on top of being assassin food. Then came the Mage update. This update basically made mages stronger in every way without any real drawback besides maybe lowering the total AP average for a game.
The champions themselves had reworks and in general buffs which made them considerably strong in damage, utility, and in other areas.
Itemization got a whole lot diverse: Hourglass and Abyssal were both buffed to be great easy options for survivability, Tons of utility was added through more CDR on all items as well as passives and actives that'd specifically benefit them, Items like RoA which added in sustain and durability, More durability with added utility with items like Proto belt, Cheap easy to acquire mana sustain from Lost chapter.
In general mages were significantly stronger now and more than capable of holding their own against assassins of all types. This of course wasn't always the case as the update definitely separated the mages in terms of power and capability. Mages like Cassiopiea, Xerath, Lux, Ziggs, Veigar ,Anivia, and Velkoz were still prey to assassins but no longer free thus making assassins harder to be successful with. The rest of the group Like Orianna, Syndra, and swain all became top tier and are easily capable of winning VS assassins now a days.
Even after it became difficult for them to find success, the Assassins had the final nail in the coffin when people still found them frustrating to play against in the times where an assassin player actually did well. So the assassin update came under the premise of making assassins feel better to play against. The assassin update ended as an overall nerf, most of the champions in the class were handicapped, AD assassins had Armor pen taken from them due to other champions abusing the stat, and a few champions were also dissected then haphazardly stitched back up with new kit mechanics that changed things weren't a problem in the first place, doesn't fit, or completely changed/demolished the kits identity. To add to all of it nothing was actually given back to most of the assassins as compensation to ensure they stay afloat.
The ones who survived were Leblanc, Zed (Kinda as he's significantly dropped) Katarina, Rengar, and Ekko. Talon is debatable as talon mains claim he's fine while the general community claims otherwise.
Leblanc survived because all they technically did was make it so she had a delay rather than any major changes to how she plays, or her overall damage.
Zed hasn't changed but he significantly dropped in winrate with the destruction of Armor Pen.
Katarina had her kit changed but received more potential damage, with new mechanics to allow more versatility.
Rengar survived because his kit wasn't really changed outside of the ult rework due to the new stealth mechanics. If anything he got significantly stronger but now because of the insane amount of free damage he gets, he's abusing tanky damage as much as Dive fighters/bruisers are.
Ekko got a very minor change so he was good before and continues to be so.
I'm not sure if I got my thoughts across better, but, if you want to read the longer version scroll up to where it says "HERE" in Bold.
#TL;DR Section/Summary
The reworked mastery system combined with items with defensive stats, utility and high amounts of free damage are allowing AD champions who build them to retain more than viable amounts of damage while also keeping several times more durability than assassins which leads to them being able to perform the same role as an assassins while doing more thus leaving no room for assassins to fight them directly nor compete against them.
The Assassin rework was done for the wrong reasons to start out with. It's premise was to fix the issue of Assassins being oppressive and unfun to play against when playing champions that the assassins were initially designed to kill and supposed to hard counter. But even after the mage update when Mages became more than able to stand against assassins and even beat them and outperform them in some cases, the update still went through. In the end it only handicapped most assassins and destroyed champions, and their identities with no compensation to make them better, or atleast keep them afloat with only a mere few survivors. One of which is rengar who is a prime example right now of an AD champion abusing free damage combined with tanky stats plus items like Black cleaver to outperform droves of other champions while still remaining unbelievably durability.
Seperate from everything else: My own personal gripe about the Assassin update is that AP assassins still haven't gotten better itemization. They still have to share mage builds which isn't tuned to them at all and they also have no access to more flat pen outside of Sorc boots and Liandries which is obviously not a viable item to build on Assassins.
Thanks for reading! As I said at the start I may have gotten valid points into the post, I may have gotten invalid points into the post, I may have gotten it all right or gotten it all wrong. If there's something I should be corrected on you're more than welcome to do so. I'm more than willing to learn and correct my thoughts on this.
On a final note, I was quite tired while typing out the latter half of it so there will probably be typo's that i missed. Hell, there's probably typo's and issues in general in the first half as well. I imagine it's probably a train wreck to read and I just don't realize it. If you made it this far you're a trooper.....
