Well for 2vs2 best combs are (Healer can always replaced by DPS):
Tier 1 (easiest to play combo's):
Assa. Rogue + Healer
SV Hunter + Healer
UH DK + Healer
Frost Mage + SV Hunter
Arms Warrior + Healer
Tier 2 (still strong but not FOTM):
Feral + Healer/DPS
Frost Mage + Assa/Sub Rogue
Frost Mage + Boomkin
Demo/Destro Lock + Frost Mage
Demo/Destro Lock + SV/BM Hunter
Tier 3 (requires more skill to play at 2,2k+):
Enhance Shaman + Arms Warrior
Boomkin + Destro Lock
WW Monk + UH DK
Affli Lock + Healer
2x Assa Rogue/ Assa Rogue + Feral
WW Monk + Enhance Shaman
Ele Shaman + DPS
Top Tier Healer for 2vs2:
Holy Paladin (playable with ever DPS)
Disc. Priest (After the buffs for Disc. its a pain in the ass to kill them)
Resto Druid (good utility and with heart of the wild they can deal some serious damage, i got around 120-150k ferocious bites at WoD season 2)
Resto Shaman (best with Warrior or Rogue, but also works good with Mage/Hunter)
MW Monk (Tier 1 and Tier 2 Combs will just train/burst you down, way better in 3vs3)
Holy Priest (just don't)