It's useful, but it's too laggy to be much use without a gang of friends around you. Once you cast it, you force the rogue's hand and open yourself up to being blackjacked/strangled.
I propose changing it so the fog remains in the room for a tick, like Firestorm. To compensate for the (slight) buff, the glowing effect could be made to last only one tick instead of ten*.
*as it does at 50
EDIT: Oh, yeah, except unlike firestorm this wouldn't follow you around. It'd be attached to the room it was cast in.
