Thought I'd start up a thread on combo's that people have run across and had trouble beating so that others could help find strategies to beat them. Post combo's that you've had trouble beating or combo's that you've roflstomped. I'll try to update this thread regularly.
Post he team comp and how to beat them in the same format as below.

Team: Mage, Pally, Pally, Rogue, Druid
How to Beat: Set focus to a pally and nuke one of them down fast (best the healer or dps one), next try for the druid to knock out all their healers. Have Healing Stream totem down to help your healer because the mage will be doing AoE.

Team: Deathknight, Prot warrior, Retri pala, Rogue/mage, Resto shaman
How to Beat: Set focus to the rogue or mage, kill resto shaman first followed by the focus, use healing stream totems (theres gonna be a lot of AoE), chain heal on all your guys if you start falling below 60% hp, kill the ret pally/DK after the focus and shaman are dead.

Team: Mage, Mage, Retri, Holypala, Boomkin
How to Beat: Your not gonna beat them

Team: Prot warrior, ret pally, shaman, shaman, Boomkin
How to Beat: Drop a shaman(healer) then boomkin to delete another dps. Once those two are dead drop the other shaman -> ret pally -> prot warrior