Warlock, Mage, Rogue, Hunter, DK dps (with tank off), Warrior Tank (with DPS off), Pally tank (with heal off), Druid heals (with feral tank off), Priest heals (with the other healing spec as off), and a shaman DPS (with a healing off)
Reason for this is because I'd like to have as much versatility in my 10-man as possible, think of the possibilities.
Druid can tank or heal.
Warrior can tank or DPS.
Pally can tank or heal.
Shaman can DPS or heal.
Death Knight can tank or DPS.
It'd be the perfect composition, suited to any encounter you could throw at it.
The Priest would have to LOVE healing though.
If any major buffs are missing, let me know (yes, I know that 30% Bleed isn't present, but none of the classes except Prot. Warriors have bleeds, and they don't even rely on it -- Rogues tend to not use Rupture any more).
This is probably the setup I'd run, since it provides pretty much every buff imaginable, if you're to stick with all the 10 classes (which I've never done, iirc).
This looks good for 10 class 10 man. I would prefer the group below if you didn't want one of each class. The only problem with mine is that it has neither a hunter or a rogue so if you happened upon a poorly designed 10 man encounter that's dumb enough to require a tranq you're screwed http://raidcomp.mmo-champion.com/?c=...00000000000000
For a 25 man I'd consider the perfect setup for maximum damage to be http://raidcomp.mmo-champion.com/?c=...00000000000000
Each shadow priest would be receiving a combined VE healing of about 2500 HPS plus JoL and Imp LotP and they all take 15% reduced dmg from all sources due to shadow form. Everyone else would be receiving 1000 HPS from VE in addition to JoL and Imp LotP. This would allow you to run with only 3 healers. Obviously its totally impractical, especially for loot, but its a fun idea