Reasons why I wouldn't be able to survive Hardcore.
Molten Affix: When I kill a molten mob that leaves an exploding core, I always think it's a life orb. I don't know what doesn't click in my head but as soon as I see that sucker drop I run to its corpse. If that was the whole point of the exploding core, then Blizzard sure got me.
Act 2: Lacunis, Wasps, and invisible snake-demons.
There's something about the grenades that the lacunis throw that's so difficult for me to dodge. Mortar mobs I generally have no problem with (unless they're also a waller/jailer/stuff), but those hand grenades have this weird timing that I can't seem to get down; mortar, I can hear and respond to quickly.
Wasps are a horrible, horrible (and ridiculous) way to die. When they spew their young at me like slow-moving darts and hit me for 20% of my health each, I just feel like an idiot. I've been using a Locusts build recently on my Witch Doctor, so part of my strategy is to run up and spray them with their killer cousins but at the same time they like to turn around at a moment's notice and throw their poison babies at my face. fuq dat sht.
Snake-demon things. I mean, they're not as bad as the first two, but they're still pretty damn aggravating. It's harder to kite since they can just vanish from my snares. In Inferno, they always jump in front of me and OHKO-stab-my-face. It's like I don't even have much of a warning to hit Spirit Walk and save my sorry-ass.
Elite Goblin Shaman Horde/Extra Health/Shielding: These things in Act 3 are like the best support characters, ever. They can res, throw fire balls, have tanky health, summon out a crew of minions, and shield things. It's like we melt the Holy Paladin's health pool and armor, Warlock's summon ability and soulstones, and Discipline Priest's super-annoying shields together and see what happens. Half the time I don't see them on my screen because I'm trying to kite the army of goblins they're surrounded by so I can't even target them first.
I mean, it's not really a huge deal but I don't realize there's a shaman there reviving people left and right until waay later.