Does anyboy really play on something other than normal/core?
As of patch 1 for IWD:EE, there is an option to turn off the damage adjustments on higher / lower difficulty settings as well as the XP bonus. So if people want to fight 3 ogres in the first Easthaven cave (instead of one) but don't want them to deal double damage and grant double XP, they can do that now.
Furthermore, in SoD, difficulty settings affect a larger variety of things than just enemy damage. Some examples include enemy combat tactics (how intelligently they pick their targets), enemy numbers (3 enemies on Normal, 5 on Core Rules and 6 on Hard, 7 on Insane), enemy group composition (3 melee opponents on Normal, 2 additional archers on Core Rules, an extra healer on Hard and an opponent with special abilities on Insane) as well as enemy spell / item use (enemies won't use their most powerful spells and items below Core Rules).