Wizards are very useful, at least IMHO. I play a monk as my main, and I do take damage fairly regularly. A wizard is usually not the first choice for a group, but if we have 1-2 extra slots a wizard is a very good option. I've found that a lot of clerics appreciate having a wiz around, since their huge burst damage can greatly speed up a fight and reduce the amount of damage everyone takes, and thus lessen the burden of healing. If things get hairy, a wizard can save the day. Not just by their evacs but by their ability to chain burn a mob to nothing very, very quickly. Just my 2cp.