A typical MMORPG is based on combat episodes(usually following each other) where player has to actively destroy NPCs(monsters usually).
If the game is combat centric, the combat episode need more polish and automation. Avoiding constant micro(replenishing life,heals, rebuff, recast).
Players need to have only high-level control(target selection(by default nearest), spell/macro/combo choice(by default current)) leaving the actual "hit/follow/target/hit" loop to AI.
This prevents fatigue and reduces player cognitive load(as RPG is not a reflex-based game, tactical combat is not suited for immersion, the AI play the RPG role better and smoother). Player should feel he directs character, but not that he micromanages it.