Good job Riot (No sarcasm)
Seriously, Riot is doing a really good job with league of legends right now. No Kappa, no good memes, no jokes, I'm dead serious that Riot has put the game in a pretty solid state.
That being said, rune reforged is about to shove itself right up the balance teams a** for at least two months but, that's a bridge we'll burn when we get there.
But, League has been trending towards a pretty solid place for quite the last half of this season. It's not there yet, but we are moving towards it.
So, let's start from the assassins rework. Shortly after it, a few important things happened. Lethality got buffed, assassins we're given counterplay, all of them got a skill ceiling buff, stealth mechanics were changed.
We entered a Meta where the 1 shot clown fiesta emerged. Black clever duskblade MF and Lucians lethality riven, garen, renekton, Darius. It was a pretty ridiculous and ADC in 2017 meme emerged.
So, the solution was buff ADCs, who honestly needed it. ADCs we're given earlier spikes and greater access to their damage faster. This rapidly became who could build the most damage Meta. Specifically AD damage.This was ok, but it made tanks and supports feel even more useless than ever before.
So they got buffs. Knights vow, new cinderhulk, bramble vest, redemption. Also some.more useless stuff like Zeke's and adaptive (which is awful). Suddenly, tanks were useful. Once Fiora got nerfed, the flood gates we're open. Among all the changes snuck in the buffs to ardent which becomes important later.
So anyway, tanks became Meta, and ruled the right for like 2 patches before one or two hyper carry buffs and things leveled out. Then they snowballed out of control.
All the previous changes to supports and tanks pushed mages out of Meta as well as increasing the sustainability of ADC against assassins AND sheild buffs. Suddenly ADCs had no means to shut them down and out current Meta emerged.
Right now, we are sitting in a solid Meta, which the only thing wrong with it is that the control mages are just a little too weak. A little. Otherwise, it's a solid Meta. And even with the current issues, we still have a solid Meta with an insane amount of diversity. Some champions aren't viable, and some comps are not feasible, but the is an array of varied possibilities.
I personally don't think the NEED for at least one tank is a bad thing though. Now, the season 4 three tanks a raka and Tristana Meta is also not fun, but I do like where we're at now. Give mages some love and tone back the rate of access ADCs have to their damage and everything will be perfect.
Actually, I'm addressing two parts of the same issue, mages can't get in range of ADCs, so it's honestly best to leave mages alone, and turn back the upfront on ADCs, in order to prevent mages from becoming super op again (Viktor Orianna Meta)
Long story short, we are where we are because of a logical progression of solutions to a variety of issues. Riot has made the right decisions all the way along, they just need to spot and cut back the single place they overcompensated which is where ADCs can early access their damage.