There are a lot of RNG mechanics that don't really seem to add much, and could be replaced with something consistent - random chance to miss attacking uphill with a ranged attack, random chance to crit, random chance to dodge, Chaos Bolt stuns and damages for a random amount within set limits, and so on. Over the course of an entire game or several games it evens out (otherwise the mechanic would deemed broken in some way and I'd assume something would've been done about it), but that's not really much consolation when you might win a game you should've lost because you rolled a 20 instead of an 18.
I'm not a fan of how carries can often grow to become virtually unstoppable after a certain point. I agree that it's possible to delay that point, and I've seen professional teams pull it off plenty of times, but I still don't feel that's an acceptable mechanic for a game that's purportedly a skill-based game... especially when the majority of the gameplay for a carry consists of "right-click a target, continue right-clicking until all targets are gone, and then right-click to somewhere else."
I'm just disappointed that, after close to 400 hours in Dota 2 (and however many hours of Dota back in ~2004-2005), the game still seems to be mostly about spamming disables and less about real, skill-intensive actions, especially when you compare it to a proper shooter like Quake or UT, or even the more indie-style ones like Nexuiz (haven't looked at the new version, talking about the old one) or Warsow, where it's literally your skill against their skill and nothing else.