I don't understand why everyone's complaining about Mundo buffs.
Alrighty, Mundo used to be the 2nd least banned champion in plat+ games, and he was that for a reason. Honestly though, I used to be a Mundo main and before the announced buffs I barely saw anyone playing him, now, don't get me wrong, I'm not saying Mundo's kit is well designed, he's too stat checky, but countering him is stupidly easy.
Let's look at his kit first:
Passive: Alright, that's some nice regen, but sadly, this regen will only really help you in the laning phase, where he kinda sucks, I'll talk about that later.
Q: This used to be the only viable part of Mundo, thanks to its spammability, but the problem is, it doesn't pierce minions, stand behind one and you're just OK, nothing to worry about. His "CC" is really pathetic, he'll never be a true tank because he doesn't have any good (or a lot of) CC, a tristana or a Twitch has better CC than Mundo, I'm more likely to see an Ashe supp than a Mundo supp because of that.
W: The problem is obvious, this is a skill which requires Mundo to have items, but it is his only wave clear, so he'd have to stand amongst minions, draining his health in the first few minutes, late - game, well, it's good but it can't be good without regen items.
E: I don't understand why this is here, literally, I don't. I'd be glad if this got changed into something else, which is why I got disappointed after I looked in the patch notes, he needs a REWORK, a buff won't solve his problem!
R: This sounds amazing on paper, but in practice? The health regenerates over 12 seconds, which is enough time to apply GW, and if you don't, all this can be used for is sustain, Mundo can't chase well with it because he barely has any mobility, you might just walk away and return after 12 seconds. What's wrong with him being able to tower dive you with his ult on? He can't spam it every 5 seconds or something.
Conclusion/TL;DR:
Mundo's kit is boring and stat checky, he needs a rework, not a buff, but the fact that he was lifted from the dumpster isn't something people should be whining about.