@Kiiath One, normal difficulty is actually really easy. If you're gettin one-hit killed, it's because your armor and health aren't as high as they could be with better items.

Two, you're simply wrong about the replaying old acts point. The change quest menu lets you go back to any quest of any act you have unlocked, and even pick a sub-point midway through those quests to start on, and then you can change back up to the later quest you were on. I go back and do the previous act boss all the time, for xp and loot. I don't know how you got the idea that you can't do that. I suppose, it does give you that warning, that says you'll lose your unsaved progress, and that tricked me for a minute too, actually. But what it means is that you'll lose any mid-quest progress you were working on, by changing quests. So just minor checkpoints. If you finish the quest you're working on, before going back in time for loot, you don't lose any progress. Even if you quit mid-quest, its usually just like 10 minutes of progress lost, and you still keep any xp and items you got in that time.

Three, health potion cooldown. It was done to make battles more tactical. In D2 you could just run into a hard fight, swing away and spam potions. If you like that better, that's your deal I guess, but the point of the potion cooldown in D3 is to make you keep moving around, picking up the health orbs that drop when you kill/hit enemies. Combine that will healing powers, and health stealing attacks, and you just have to think more about how to stay healed, it's not that hard. I'm almost done with NIghtmare difficulty now, and I haven't even used a potion in half of the last act. And no, I'm not using obscenely over powered stuff from the auction house. Everything I'm using was dropped as random loot, in game, playing solo. You just have to strategically combine skills that steal health, and keep moving to pick up the health orbs, only relying on potions in a serious 'oh sh!t' situation, to prevent dying long enough to run away.

@Pelezinho777 @erwerman not gonna happen any time soon. its not just a crack that diablo 3 will need. fundamentally aspects of the gameplay such as damage and loot drop calculations are completely handled server-side. there will have to be pirate servers made, and even when they come, they will be crappy, like most pirate servers for online games.