I have 2 lv 80 Shammy that I want to boost to lv 85. The other 3 Accounts have 2 lv 85 shammy and a Pally. I am wondering what would be the fastest way to boost the 2 lv 80 Shammy to lv 85? Questing or Dungeons? Would I need a tank or can I reasonably do DPS (4x) with Pally heals?

If I do need a tank, I can pull in a DK blood for the tanking and then drop one of the lv 85 Shammy