I mean, he's always been annoying to play against yeah, I knew some scrub would eventually ask for nerfs for him. I didn't expect it to be before the buffs even came through however. So here goes:
-First of all, he's so unbearably weak right now, it'd take far more than this to break him. He'll maybe become viable, and you'll have to dodge more Qs on the toplane, big deal.
-Second of all, the decision making regarding his ult just became harder, why? Because they removed the reduced cooldown when he feasts on minions, so if you ult a minion you basically just said the enemy laner: "Hey bro, my ult is on cd for the next 80 seconds, feel free to all-in me, you'll win. You can also zone me off farm and sustain too." But if you don't ult a minion, you're losing out on valuable stack-time since it takes so long for the ult to come back. If you save your ult for champions all through the lanephase and go into midgame with no stacks, you'll get eaten alive from the lack of HP (Cho is balanced around the bonus HP on his kit you know?).
-Third of all, Cho has never, EVER built full tank like Sej or Voli do, and he won't do it either starting this patch, why? Because his base damages are MEH, but his scalings are outstanding, so if you wanna deal damage with that QW you need to build AP anyways, so if Cho wants to remain relevant, he will be making more use of that AP ratio than that HP ratio. The ult damage isn't going to change a lot really.
-Fourth of all, the only thing getting a buff here is his ult, you know, that melee skill on a champion with no gapcloser and whose only CC is widely telegraphed? Any ranged champion with a couple neurons will be able to dodge the Q and kite him to death like the buff wasn't even there anyways.
-Fifth of all, it's not even a real buff? It takes twice as long for him to stack now, and his stacks give less HP. So if he's not snowballing off champions, it's actually a heavy-handed nerf to his early and mid-game.
-Sixth of all, Cho is a burst champion, but Riot just did a nerf of burstiness in general in the game with the mastery changes. This will actually affect him significantly, since the hardest part for him has never been being hard to burst but managing to have actually relevant damage.