Trio Suggestions

[Reubin]

I'd be tempted to go with

Shadow Knight
Cleric
Enchanter

That gives you a tank who can generate great agro/snare/feign death pull, crowd control/mana regen/slows/haste, best healer in the game/rezzes/lull.

This group would be ideal as the basis for a larger group by adding DPS. With the "holy trinity" covered it would make finding group mates extremely easy if you want or you could function well as a trio. It would work well outdoors or in dungeons. It would excel against undead. The only negatives I could see is that the SK has a xp penalty so they would level slightly slower than with a warrior and they wouldn't have access to ports. But the SK's abilities and snare more than make up for the xp penalty and ports can be bought or druids could be befriended.