I dont run a Dk but a pally tank with a resto shaman and it makes heroics a heck of a lot easier, sure it can be done with 4 as dps and throw a small heal here and there. Earth shield and healing stream totems usually keeps my palidan topped off until i reach a boss

heres my resto shaman spec

http://www.wowarmory.com/character-t...or&n=Udderduum

i still specced into elemental and if you look the only things im missing that would make a difference would be Elemental mastry and lightning overload. reason i say this is sure, im getting less dps from one character but if your ripping through trash like tinfoil why not make some of the boss encounters less stressful with some extra heals. Specially with riptide, think mine ticks for 1k-ish