Melee DPS is very high and quite impossible to substitute. However, most encounters have some kind of melee-unfriendly thing, which forces you to reduce their number. Without considering tanks, more than 5 melee DPS usually is bad.
Well we tried TK with 2 melee DPS parties last time, was quite funny, VR died in like < 5 minutes, Kael'thas was down in like 2 pyros, but they nearly all died when we got a couple of consecutive Flamestrikes near the boss, forcing them to move and stop DPS.
Worlde - Prot Paladin
Darkworldie - Tank DW Frost DK
Uord - Prot Warrior
Huordie - Feral / Resto Druid