Flamy507's short video about bosses that are only reachable via a giant elevator is so true it hurts. No matter how easy the boss seems, if there's an elevator, it's almost certain that it will kill everyone.
He uses World of Warcraft (remember Serpentshire Cavern?) as an example, but it's probably the same with every game or MMO with funky in-game physics and the occasional lag.
The Elevator Boss by Flamy507 [YouTube]