That's an issue with repeated play of static quests, not direct features of those traps or situations.
I'm sure many people have been in that situation and have died to the elementals in Rainbow for lack of foreknowledge of the quest.
Also, I'll say that any object that turns out to be a mimic should be restored to its original, intended object, after the mimic dies. It shouldn't rob a party of a chest, collectible or shrine if they bother to kill it.