Blood DK Gear questionFollow

The best dps stat possible for a DK is strength. Point for point, it will give you the highest dps. After strength comes ArP because most of Blood DK's damage is physical, so you'll need to be able to pierce the high armor of raid bosses. Hit/Expertise/Crit comes next. They are important, but they aren't quite as good as strength or ArP. Obviously try to make sure you are hit capped though, because being way below the hit cap will totally destroy your dps. Expertise is a little less important if you remember to attack mobs from behind whenever possible.

Haste and agility can pretty much be ignored. Haste doesn't affect rune cooldowns, and agility really only adds to our crit, and crit rating does a better job of it. Most of the good DK dps gear has plenty of stamina on it as well, so you should be fine on health.

As for gemming, +str gems are always best, but use 2 Sovereign Twilight Opal (+str/+stam) or it's epic counterpart (idk the name lol) to meet the meta requirement for the +crit rate/+crit damage meta gem. Also, in general, don't worry about socket bonuses. They are pretty useless for the most part.