Melee: Warrior
Ranged: Warlock
Healer: Shaman
I don't know of a single class that is overpowered, but the Shaman-Warlock duo seems to be quite formidable when put in a three's team, as they have amazing synergy and seem to work with any sort of team composition, whether it be another melee DPS, ranged DPS, or healer.
Frost Mage. Always Frost Mage.
https://www.hotslogs.com/Player/Prof...ayerID=1579599
"MMOC forums let me keep my job again. Whew." -Greg "Ghostcrawler" Street
I don't think there's one single overpowered spec, there's just a lot of really annoying ones. Like hunters. Argue all you want they're not op in 3v3 but those random whacky 300k chimera + aimed shot combos scream 'skill' -- as much as warlocks with ten million fears or warriors with ten million stuns.
I'd say top 3 is warlock, shaman and druid. Purely because of the annoyance factor.