Note: My DK is 60. I don't have ANY working knowledge of DKs besides playing with them in my raid and reading a lot about them.
The Story: A new DK in my guild was invited to Naxx last week. He was specced blood, and did between 800-1200 DPS. Looking at his gear showed the first problem; his gear choices seemed to be "anything with plate is good." Most of his items were green; his trinkets were from the beginning SK quests, and half of his items had parry, dodge, or defense on them. His spec seemed ok, but I remember hearing that blood is the most gear-dependent spec, and that frost was the least. I recommended he switch to spec, looked up a spec from Elitist Jerks, and gave it to him.
His spec: http://www.wowhead.com/?talent=jfVMVZGMxtIxdRhoVosx
From this discussion (Frosty DPS discussion).
Yesterday, with a few upgrades (but not nearly enough, IMO) he ran heroic UK with some other guildies. He hit around 1.2k DPS... not a huge improvement, although a bit of one. After, the priest healer in the group asked me who gave him the spec, and I said I did. He said it had a few points misplaced. Perplexed, I looked up Elitist Jerks again... and noticed a completely different Frost DPS discussion: Freezing Hell Over: Frost DPS. This thread had three specs, including another 17/54/0 spec, http://www.wowhead.com/?talent=jfVMVZGLxthxdRhoVost.
I'll admit, I'm lost on where to look and what to choose to help this guy. He is VERY receptive to advice, but seems to not understand almost anything about his DK (his main is apparently an elemental shaman). Was I right in recommending frost for him? Or would unholy be better (it might be in 3.1, but I hear Scourge Strike is a little underwhelming right now?).
His armory: http://www.wowarmory.com/character-sheet.xml?r=Sen'jin&n=Dreadnaughte
Additional notes:
1. His spec has apparently changed once again to some strange combination of things. It is in none of the EJ threads.
2. Looking at his gear you can get an idea of what he used to have by looking at his rings, leggings, and trinkets. The hands were a hold-over from our Naxx run; even with the int and the fact that they're mail they were a big upgrade for him. He obviously still needs enchants and gems. He got a new helm, but I think he should go for the SPiked Titansteel, because of the meta.