this is the frost DK macro I use.

I forget where I got it, but it works 95% of the time.

#showtooltip
/castsequence reset=3/combat Icy Touch, Plague Strike, Frost Strike, Blood Strike, Blood Strike, Obliterate, Frost Strike, Obliterate, Frost Strike, Obliterate, Obliterate, Frost Strike
/cast !Rune Strike