I think the Healer+4 DK's is still your best bet for a 5's team, though Healer+4 Warriors and DK+4 Rets are close. The problem with the Warriors and Rets is that you don't have any defensive immunities that really destroy people. With the DK's you can Deathgrip while you have IBF, Lichborne and AMS up--Which makes you basically immune to every CC (except disarm) for 7-12 seconds. It's enough time to force a kill if you splash blanket Strangulate their team.

The Warriors will Charge-->Recklesness-->Brostorm. The damage from 4x Warriors would be insane--The problem is that once Brostorm is on cooldown you're much more easily kited and CC'd than the DK's or the Rets.

The Rets do take that ramp-up time before they're doing maximum DPS but being able to remove snares/roots from yourself is pretty amazing. If Wings makes it off the PTR being undispellable and not spell stealable... Yeah, they'll probably be worth it, especially with 10 sec WoG.

I think the problem with the Shaman team is still mana/survivability. Blizz really pushed for all of the caster DPS specs to not be able to offheal at all basically. That neuters the Shaman imo~.

Edit: @remanz: Lichborne is 12 seconds of fear immunity and can be used once feared.