I have an 85 shaman on one account, an 87 shadowknight, and a 90 bard on the other... Which one with mercs is gonna be more viable? Shadowknight + Shaman + wiz merc + wiz merc Or Bard + Shaman + wiz merc + tank merc?
Hrm SK is gonna be a good puller + tank. Bard is gonna make you rely on merc tanking but have massive pulling, give CC, large ADPS etc. I would almost say it's a toss up and based on where/what you were fighting.
Depending on the SK's gear and AA, I'd lean more towards him. Bards are nice as group support but I wouldn't box one just for grouping. You can probably find another player (ranger, enchanter, bard) to fill the CC spot if you're doing things that require it.
Bard and Shaman is overkill on utility and you will lack dps and tanking. SK + Shaman is the obvious choice.
I like the SK + Shaman , but you might pick one healer merc to take some pressure off the shammy healing.