My opinion is in line with Zusuk. As it is now, I think it might be too much of a hassle and slow down the pace of the game. However, if you did create a custom GUI/Client that allowed mouse pointing to choose which target a spell/effect would be cast on then it would be much easier and fluid.
Another idea might be to represent multiple same type mobs in groups rather than list each one individually, and to have blasts/splash to affect that group only, or if the spell/skill was high level then possibly other mobs/players/groups in a room.
Mobs would be represented as singular or plural and there would have to be new descriptions put in the mob OLC menu.
A darkling minion scuttles around here.
A swarm of two darkling minions conspire against you.
Might clean up rooms a bit though.
