4 holy/disc priests plus ???

[Owltoid]

I'm really having a tough time deciding on my fifth toon, or if I should even have a fifth toon.

DK
pros - strangulate, death grip, freeze ranged opponents with ease, tough to kill
cons - no real synergy with the priests, though 13% magic debuff could be used.

Mage
pros - freeze everyone in place for the AoE storm, decent synergy with buffs, insta cast AoE to go along with priests, nice range for sniping with priests
cons - glass cannon, would require a transfer from another account plus some extra leveling (my situation specific, obviously)

Shaman
pros - fear protection to go along with fear ward, root people in place, good burst, probably more that I'm not thinking of
cons - makes group more stationary

Moonkin
pros - decent buffs, typhoon and starfall helps position enemies, roots could be used to lock in place sniping targets, decent "tank" in PvP (big target that everyone likes to go for), could get badges with the priests by joining as a tank in PvE
cons - no spammable AoE so not sure what the moonkin would be doing during the swarm phase

Destro Warlock
pros - destro can stun for the swarm phase, hellfire could be used with the amount of healing going on though it's not mobile (I don't think), small amount of buffs, good burst potential
cons - would require an account transfer, doesn't feel like a great synergy between the teams

Fifth Priest
pros - more healing, more AoE, perfect synergy which could enable me to use more priest specific abilites since I'm not working about diversity
cons - lack of additional buffs

Playing five toons instead of four
pros - more damage, more coordinated burst
cons - more responsibility in BGs, have to drop a member to have a friend join, can't gear in PvE quite as easily (have to rotate)

The swarm phase is probably the most important. A mage or fifth priest probably handles it the best. A DK can help with the hunters that seem to be giving me the most problems.

Any ideas?

[Svpernova09]

I'd go Destro Warlock.

[Oatboat]

Mage for a couple reasons.
The main one is Free Water!!!!!!
Second like you said Frost Nova and Arcane Explosion
Smite and Frostbolt should have same cast time with spec. 2.0 seconds i believe
Shadow word death and Fireblast

[Maxion]

Arcane explosion goes very well with holy nova.

[ghonosyph]

I'd likely go with a tank that can swap roles for pvp, druid seems the best choice here with dk close second, as dks offer a TON of control

[Multibocks]

I'd do 5 x priest in pvp and then keep a tank around for pve.

[Owltoid]

I'm really leaning towards a mage, though I don't want to pay to transfer one from another account (not to mention they'd be level 60, which isn't a huge deal, but I am getting tired of leveling).

Edit: I just watched the video again, and I'm starting to agree with Maxion. This group grows in power exponentially. If I had a group of 10, and all 10 were affected by holy nova, then it would be even better. So why not maximize the size of goup? When I have enough talents to get Aegis (mini bubbles), then it will be even better! Ultimate survivability incoming...

[Mokoi]

plus the mages barrier can go with the shields on the priests.

but fear and aoe will really ruin this team if done even brainlessly.

Besides, aren't you rage quitting over the talents? lol :P

[Owltoid]

My god, please quote anywhere that says I'm cancelling my accounts! The closest I've came is saying something to the effect of "I'll have to wait and see about the changes, but if they remove a part of the game I enjoy the most then I may move on." Somehow that has turned into Blizzard sucks - I'm taking my ball and going home. I have a wait and see attitude, but that doesn't mean I can't also be pessimistic and upset at the lack of customization. Who knows, as ive stated before, they may build enough diversity into one tree that eeryone won't be cookie cutter - without knowing my guess is they won't. Hopefully I'm pleasantly surprised.

[Owltoid]

The only team that can truly handle fear is shamans. Priests can do it decently well with fear ward rotations and cycle dispelling. It's not nearly as nice as totems pulsing every half second, but it's better than lots of other teams (like moonkins).