The problem with Diablo II was not the immunities, as you were meant to work as a team (thus have someone with you who complements you). The problem was how broken bugs made hell mode. Tomb vipers by nithak deal over 50000 DPS which is enough to kill any non pallidin (as pallidin can block 90% of hits from it) in under a second. Dolls dealt their enhanced stats on death meaning that stone skin extra strong corperal could deal over 10K unblockable physical damage which only really strong builds could survive (this was fixed, most builds will survive atleast 1 doll before having to respawn). Mana burn (any sort) deals over 255 times more mana damage than it should on high difficulties when spawned on enemies with multiple buffs meaning that even 10 damage causes you to lose 2K mana (no build ever has that much). Most notorious of all was the wisps, who have crazy ligthing damage and mana burn who deal their melee damage ontop of their spell damage (causing tens of thousands of lightning damage). You also get kicked all the time as summon mancer due to too many skeletons or if you fight too many badies at once.
Those are a few of the mistakes...
WC3 should still be limited to 8 MB.
