Zerg team moving to a holy trinity team

Current zerg team: Palatank + 4 meta warlocks.

Im looking at moving to a holy trinity team as the locks just dinged 70 and I was able to zerg BC non heroics with the crew nps. With the lvling and gear replacements that WOTLK has presented Im thinking of reworking the team.

currently @70 I can run pally+4locks or pally 3 locks +mage.
Im thinking of dropping a warlock for a resto shaman (must lvl the shammy team lol)

So to the multiclass boxers out there what is your preferred healer and why?
Would it be worth dropping out another lock and running paladin, warlock, mage, boomkin and resto shammy?
Is the mage worthwhile to bring into the team and drop one of the locks?