DK'abilities are based on rune and rune power. There are 6 runes, 2 blood runes, 2 frost, 2 unholy. It will take 10 sec to cool down after the rune being used. Rune power is calculated by costing of rune. The frequent use for the abilities is: cast rune-base ability first, then the rune power ability. What we need to concern is, how can we use the rune with the best result.
Icy Touch - Plague Strike - Heart Strike x2 - Obliterate / Death Strike - Death Coil x2
Common attack method
Cast Icy Touch (1 frost rune) and Plague Strike(1 unholy rune), which can disease the foe with Frost Fever and Blood Plague. Two times Heart Strike and Obliterate once should be followed. If DK's HP become low, Death Strike instead. Now DK used all 6 runes. Since DK already get full rune power, he can cast Death Coil twice. Then this circle continues.
Blood DK has great cruising power. Always Blood DK need not eat or first aid. Hp can be healed by rune tap, Bampiric Blood also Bloodworms(passive).