My rotation is IT, PS, Pest, DS, BB and Rune Strike whenever its up.

On paladins I have a click macro that does JoW/JoL, DS, CS, Cons, HoW, DP, AT. And a macro that casts Instant FoL on the DK like this:

#showtooltip Flash of Light
/cast [@tank] Flash of Light
/stopcasting

So it only casts whenever the AoW proc is up. AoW procs constantly so its not a problem keeping the DK healed. You also have a lot of healing talents in the blood tree you can use.