2v2 tactics vs DK+healer. need advice!

alright, so me and my resto shammy friend have been playing 2v2 for 3 weeks now. we got 2011 rating and then lost 100 rating in one night. from there we keep moving around 1900-1950.
our main issue is DK+healer.
there is just seem to be nothing we can do. we have tried every possible tactic we couldve think of, but it doesnt even matter what healer it is. holy pala is ofc the worst, but resto druid, resto shaman, and today it was a disc priest - we mostly lose to all of these set ups.

the DK can choose who he wants to go for, or he can just switch between me and shammy as many time as he wants. it doest realy matter. we both die a horrible death eventualy.

anywayz, i would realy apriciate any ideas about possible tactics.
i got so depressed at one point i even left my shammy and tried a bit with a pala (hence my low PR atm).

p.s: i posted this in the hunter forum originaly, but i think i might get better input here, or at least i hope so.