Long ass post about the balancing situation regarding Jayce
This post is intended mostly to request some changes and bugfixes for Jayce, and it contains some information about, and my point of view and opinions about the balance history on Jayce (since early season 3). I have been maining him pretty much since i started playing lol, in late season 2.
Jayce was a bit of a sleeper pick before Muramana existed (however, Manamune did exist, it just wasn't as great before it would upgrade to Muramana), that was beack when tear stacked when Jayce switched stances.
When RIOT added Muramana Jayce became a REALLY strong pick. This was due to Muramana being such an efficient item on Jayce, partly because it stacked when he ulted, and partly because Jayce can proc 4 Muramana on hits in a row with his ranged W (Hyper charge). In late season 3, RIOT changed a couple of things to balance Jayce. Tear could no longer stack off Jayce's ult, and the cooldown on his ranged E (Acceleration Gate) was changed from 14/13/12/11/10 to 16 at all levels.
In season 4, however, Jayce was a bit of a sleeper again. Sure, he wasnt the poking monster he had been in season 3, but he could still oneshot anything except a full tank with one full rotation of both his kits (Shock blast - Hyper Charge - To The Skies - Thundering blow). Jayce's only problem back in early season 4 was that so many things could kill him before he could kill them. Well, that was before RIOT made some huge changes to Exhaust, and the itemization for Marksmen.
When Exhaust got changed to work better as a tool for negating burst, Jayce could actually start duelling pretty much anything, but it mostly made him able to duel assassins and burstmages in midlane. And the itemization changes to Marksmen really favoured Jayce, because Manamune got slightly buffed. And lastly, (this last part mostly affected soloqueue) Infinity Edge got buffed, and so did Youmuu's Ghostblade, and this made Jayce able to do some serious critting. Let me put it this way:
If Jayce builds Manamune, IE, Ghostblade, he has 40% crit chance. If he autoattacks a target, and resets his autoattacks with his W, he can get 4 autoattacks in a row with capped attack speed. The latter three of them will deal bonus damage if Jayce has 5 points in his W (and lets assume he does). And since he has 40% crit chance, and the IE passive, he is likely to crit 1 or 2 times out of 4 autoattacks. If one of his enhanced autoattacs crits, it would deal 1,32,5 of his base AD. If he has 300 AD, that would be over 900 physical damage in one autoattack when Jayce has 3 items. Add the damage from the other autoattacks, and the muramana proc, and you will end up with 900 more physical damage from his other autoattacks, and (lets assume Jayce has about 1600 mana) 360 damage from muramana procs (thats 0,97^41600, do the math if u want to, I rounded down). So thats pretty much 1850 damage with 4 autoattacks. And its not unlikely to crit twice with 40% crit chance, which would basically just be silly amounts of damage.
Most recently, RIOT made a change to Jayce's Hyper charge that you can read about in the 4.21 patch notes, because i don't feel like explaining it here, especially since it wasn't a direct nerf to Jayce's overall strength, it was just a small change to make Jayce unable to basically use Hyper Charge twice without cooldown.
TL;DR Jayce has been OP a lot, and his kit is really strong.
Ok, so Jayce is still strong, and ive seen some PBE updates that I am assuming are going to through to patch 4.22, and they are going to change Hyper charges damage scaling from 0.7-1.3 to 0.6-1.0.
As i have explained how Jayce could deal TONS OF DAMAGE with a single spell, which ”coincidentally” is the spell that is getting nerfed, i feel like i shouldn't have to explain why they're nerfing this spell again.
So what's my point? Well, here's my first point: Currently, RIOT are having some obvious trouble in balancing Jayce, and I totally understand why, it's the same problem as Lee Sin. Jayce has so many strengths to his kit, that it is really hard to keep him constantly balanced. And Jayce's kit's strenghts have been really overwhelming at times, especially during late season 3, (at which point he was the strongest champion in the game, and he could 1v5 with poke if he got ahead and had blue buff) and late season 4, at which point he could oneshot squishies with a single 4 sec CD spell (but at least he can't 1v5, good job RIOT!).
My second point is that I'm aware about the situation about balancing Jayce, but I'm not completely satisfied (which is why I'm writing this post), and I have some criticism and suggestions.
First of all, Jayce should get some changes to his kit.
His ult NEEDS a buff. It's not worth putting levels in it until you're level 16. The armor shred that you get on the first auto in cannon stance is not reliable enough to be useful, because Jayce doesn't change stances that often, so you almost never proc it on champs. I suppose that you could argue that Jayce players should try to use it more often for higher burst, but even then I would say that it's not a solution, since you would have to go out of your way in switching stances to be able to use it. AND the damage increase from higher levels in W is WAY better (it will probably be that way even after the next nerf), and putting levels in E is better than ult because of the movespeed increase for Acceleration Gate, and the damage increase and CD decrease for Thundering Blow. So my suggestion is that regardless of what you do to his kit, make the armor shred only proc on champions so that you cant waste it on minions. Maybe give it an internal cooldown that doesnt require stance switching? Also, i would like to argue that since his W's damage is getting nerfed, you could give jayce a slight increase in Cannon Stance autoattack range from putting levels in R.
One more thing that imo really needs a change is Jayce's thundering blow mechanics. It's buggy as hell. If i use it on someone, and they flash while the animation of Thundering blow is going off, they will have blown flash, and still be knocked to the same place that thundering blow would have knocked them to if they didnt flash. And, if you cast it on a target that becomes stealthed in the middle of the cast animation, the spell gets cancelled. So please RIOT, make thundering blow instant, like Lee Sin's ultimate (or any other bug-free knockback PLEASE PLEASE PLEASE).
Speaking of bugs, both Shock Blast and To The Skies bug a lot too. Shock blasts sometimes just disappear without dealing damage or granting vision. And To The Skies fails to jump over walls a lot, the spell gets cast on a target on the other side of a wall that Jayce is standing next to, Jayce jumps into the air, the spell goes on cooldown, but Jayce doesnt actually jump to the other side of the wall, he gets stuck...
Im going to end this post by making it clear that I am aware that Jayce isn't a high priority for gameplay updates, but i really think he deserves one, to not fall out of favor, which he easily could, considering the overall nerfs to his kit during the last year.