Mixed groups are truly powerful; I'm running a group that consists of an unholy Death Knight, a protection warrior, 2 BM Hunters, and a Holy Priest. I haven't ran into anything that the group can't trash. Even some of the earlier fights that I had difficulty with as a team of 4 shaman + paladin really became trivial with the mixed group. One fight that comes to mind is the Nazan fight in Ramparts. When I was around 62'ish with my shaman + paladin team, I would typically lose one or two people once I got the fight down; just learning the fight and dealing with the huge AOE damage was not a trivial task (I probably wiped 9-10 times learning the encounter); I honestly believe that the ramparts was the *hardest* (yes, even harder than Sethekk) instance that I ever delt with as a multiboxer with the shaman + paladin team.

Now, on the flip side of the coin, I did the ramps with my mixed group. On my first attempt I simply walked through the encounter, no deaths, had everyone attacking. On my 2nd attempt at it, I killed Vazruden with my team, and then I let my pets kill Nazan. Needless to say, they walked away with 80% hp each (1 core hound, 1 devilsaur doing the fight) - they needed 0 heals, 0 buffs, etc. It was amazing.

With all of the amazing capabilities that a mixed group brings to the table, it's no wonder why an encounter can be trivialized by adding multiple classes. My 2nd team (the other half of my 10-box setup) is fairing well too; it consists of a Protection paladin, 2 Arcane Mages, 1 Resto Shaman, 1 Balance Druid. Encounters are a little bit tougher with this group (as you can imagine), but the dps is much higher with the 2nd team than the first. It's also nice not having to worry about agro as much as with my first team (1 tank = easy agro control ... 2 "tanks" + pets = easy agro control once you get the macros down for it).

Cheers.