I would stay as far away from 2s as i can as a holy paladin healer, i mean it can work with a decent feral/dk/dh but you will get outcomped in 2s by every mistweaver/restodruid/discpriest healer/x team at somepoint along the way.
Holy paladins are only good in 3s because of their strong support cd's for a caster/melee cleave, when you dont score a kill in the first 5 minutes its basically gameover, when 2 melees connect on your paly and he got no wings left for the healing output hes basically dead.
DK/hunter/holypaly was a strong comp in past expansions, i dont know how good it is now but given the state of survival hunters i think it can work very well.