I say to hell with cast and wait. just team up with another wizard and one
tank. get tank to start it off. and you blast while other wiz cast root. the
mob wil surely go for ONE of you. at this time, if you get hit, the other wiz
stand max distance from u and blast while u melee the mob. the mob will
eventually leave u and go for the other guy, and then u blast while the mob is
running to him and he root the mob again, if root is resisted, doesn't matter.
ur blast will kill mob anyways.

Even better if you can find 2 other wiz to group with you. 3 wizzies kick so
much ass. to hell with those worthless tanks. one of you root to start and
others blast to start. one of u wil get tagged. others blast , mob will
switch targets, others keep blasting. mob will run around doing dick all while
everyone blast from a triangle position max distance. mob will be dead
quickly. get the person who the mob is running to to root, if root is
resisted, another guy from other position to root. if its red and root just get
resisted all the time. forget it. just keep blasting hehe..

i killed night stalker in east karanas who is red to me this way and i was only
lvl 13 at the time. and night stalker resist root every time but shock of
lightning can still hit for 31 dmg. This strategy also worked at lvl 8 for me
killing wisp, grizzlies. and also ghouls are lvl 12.