Let me make it easy and list the classes that groups will invite:
Alb support - cleric, rejuv spec friar for healing only, and heretics
Mid support - healers and shamans
Hib support - bards and druids and sometimes wardens
Alb casters - all but necro
Hib casters - all are fine with recent patch love
Mid casters - all are fine
Alb tanks/hybrid - minstrel and merc. merc is really the only alb tank that consistently gets groups
Mid tanks - savage/zerk/skald/valk
Hib tanks - BM/champ/hero/vamp
There are other classes that aren't on the mauler and necro shit list, but they aren't nearly as desired. And it usually takes a group of friends to run those classes. Like caster thane. I might have missed a few, but this list covers plenty of group friendly classes.
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Devaster
Shadow Syndicate [-S-]
Chesapeake - Ultima Online