Play whatever you like. Rogue is the toughest of the four, because they are gear AND group dependent while being unable to solo to acquire said gear. The other three should be just fine and are good pickups for any group.
Running both an an enchanter and a monk won't hurt: when one can't find a group or you don't feel like soloing on it, you can hop onto the other. I do that with my wizard (33) and ranger (40)
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