Suggestions
I have a few suggestions, coming from an experienced DK player, I found a lot of issues with the ability priorities.
Blood DKs:
-Simple Rotation:
-DeathGrip(Only if target is 15-25 yards away, else save it up for when they run, rogues spring, mages blink, hunters disengage, etc),
-After the DG opener or if they're closer than 15 yards, ALWAYS lead with Chains Of Ice as it infects w/ frost fever as well as slows em down (Don't use Icy Touch at all)
-Death Strike until you run out of runes for it, and with Runic Empowerment that could be a while
-Once Death Striks is on CD, then drop a plague strike (Heart Strike deals additional damage based on plagues, so having both plagues up is kind of useless until you get your death strikes out the door)
-Alternate between Death Strike on CD and Heart Strike, and refresh plagues when needed.
-Primary nuke ability should be Death Strike, I noticed it spamming Heart Strike a lot, Heart Strike should be used while plagues are up and Death Strike is on CD
-The key factor in PvP'ing with a blood DK is their self healing abilities, when the DK hits 50% hp, the primary ability you strive to use should be Death Strike, and 99% of the time, you can couple Blood Tap with Death Strike to get the runes you need for it.
More later on Frost and Unholy, I have to work atm.