If I've understood this crash log then the Adrenaline Seeds caused the crash when dropped. Found them in a chest in one of the Roguelike Dungeons(I think that's the mod, the dungeon that's a castle tower made of snow and quartz), was swapping inventory stuffs with someone and the game crashed shortly after I dropped them. They're not in NEI, which makes me think they're not meant to be in use.
http://pastebin.com/embed_js.php?i=ufXWZYWU
Is it your intention for the Infernal Mobs to be utterly ridiculous?
I've come across mobs with what must've been 7 or more modifiers and the only way past is to either box them in somehow(if you're lucky and they don't have an aoe effect) or just walk away and hope they depsawn. Something with 2 or 3 effects is manageable if you're careful, and 5 effects might make a good boss/rare type.
When DoTs start stacking up(including ones you get from hitting the enemy, not getting hit) as well as stuff like melee weapons sticking to the enemy, constantly being picked up and slammed down with another couple of effects thrown in for SnG I feel like it stops being challenging but fun and turns into challenge for the sake of it.
It might be worth adding a part to the Gilded Iron quest to craft some armour. 16 bars is just enough to make a helm, chest and boots and it seems to help keep you warm in cold places and cool in hot. Not a bad stepping stone on your way to better armours.
I don't know if you'd want it in a similar place as Gilded Iron but a nod towards the dungeons wouldn't hurt. We found a nice bit of Pneumaticraft stuffs in there which is one of the next set of quests. It should definitely come with a warning if you do, those places are
scarey
Can't wait to try out the new patch