Turn-based combat is necessary in PnP... but if you do it in PC games, you're basically just clinging to a primitive tradition.
Regarding my initial post (including creature/summons part); if you have a party, turn-based is necessary in order to have direct control rather than delegate some members to a party AI.
Why do I want direct control?
I could want to play a game, rather than watch it play itself.
I could also be better at making decisions than the AI. D2:ED isn't out yet, but games with party AI have been released. Unless giving commands fast is better than giving the right commands for the situation (real-time versus turn-based), experience indicates HI is better than AI.
