A while back, I heard that its possible for people to do the spell quests together as long as they are in the same school. I never tried myself. Is it true..? I've been stuck on the quest for spinysaur for a while now. I've tried and tried again with no luck. So if this really is true, it can be my last resort.
I think it probably depends on the quest, but generally I would say no- at least on the final fight. These instances are often single person instances. You could probably do the rest together if you really wanted though.