Beth'tilac: Unlikely. With the DK/Hunter group, you might be able to have both people survive P1, but the amount of damage in P2 will almost surely kill you and your tank will die to the debuff. Healer/Hunter would have trouble burning down all of the adds in P1 without OOM-ing.
Shannox: Impossible with a Healer/Hunter, very unlikely with a DK/Hunter. Face Rage will be impossible to handle with a Healer/Hunter, and relatively hard with a DK/Hunter. You might have the burst to get Rageface down before he does one, but I doubt it.
Lord Ryolith: Probably not, but worth a shot. If you have enough damage to steer him properly, the DK should be able to handle the adds. That said, good luck surviving the P2 damage. I would think this impossible with a Healer/Hunter group due to damage.
Alysrazor: Maybe. If your DK or Healer are good enough, they can tank two birds and collect all the worms while you do one of two things. Either you fly while the DK handles everything on the ground or you clean up adds and take pot shots at Alysrazor with your healer. She does do quite a lot of damage on the ground, but you might be able to survive it.
Baleroc: Impossible. Due to the crystal mechanic, I doubt he can be done by any fewer than 4, if not 6.
Majordomo Staghelm: Maybe. Leave him in Kitty form, you won't have a choice, and burn the adds as they spawn. Hope you can burn him down before the entire floor is covered in fire.
Ragnaros: If 10 DKs can do, there is no way in hell you're going to duo him. Sorry, but you'd have to get very lucky with traps, Sons of Flame, Seeds, etc. This is far and away the most difficult normal-mode fight of Cataclysm, and I doubt it will be duo-ed any time in the near future.
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