I need some advice about a friend, who frankly has the worst/laziest DPS I could possibly imagine for his class, spec and gear level, even if he was just spamming buttons mindlessly.

Explanation:
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Friend A plays an Unholy Death Knight, after being bought the game by Friend B. Both I and Friend B have bought, given and crafted gear for Friend A, up to the point where I can estimate his item level at being between 375 and 380 (he has a few Hour of Twilight Heroics, some Valor gear, and some crafted 397 gear). We have ran him through so many dungeons it isn't even funny, and his DPS, is frankly terrible. At that item level he manages to get MAYBE 15K DPS at any one point (it's usually closer to 10K, if that some times). Friend B went out and found Friend A the optimal spec, and a fairly simple rotation to help improve his DPS. At item level ~330, I can regularly outdps him on Fury Warrior, and I can't for the life of me figure out how to get his DPS to go up any further than me and Friend B have already tried to do. Our plan was to eventually take him into LFR and try and get him some tier gear, but we're actually afraid to take him into it because we think he might get kicked out of that frankly toxic environment just because of how bad his DPS is for the gear he currently has.

Now, here are the problems me and Friend B have identified:
1) He craps his pants whenever he takes any damage. We have no idea why. He just does. He's playing a DK, we've told him he has enough defensive cooldowns to get through incidental damage on fights.
2) He lacks awareness of any kind sometimes. Seriously, we've asked him why he was just standing there in some boss fights doing nothing, and he replied that he was texting. This is not a rare occurence, it happens nearly every other fight.
3) According to Friend B, Friend A is just lazy, despite the fact that Friend A recently finished his first year at one of Britain's best and most strict universities.

I just don't know what to do. He's playing a DK, a class that can frankly do decent dps through mindless button-spamming (I'm not ashamed to say that 50% of the time I'm only half following my rotation/priority system and am really just spamming buttons, although I am getting a lot better/luckier at managing a rotation continually through fights).
It is honestly getting to the point where me and Friend B are just thinking about dropping the niceness (we've been okay with it so far since in the past he's been alright and we've blamed his lower DPS on lack of gear rather than anything else, but now that there's no excuses left it's just irritating) and confronting him about it.


Sorry for the wall of text in there, but I needed to vent that. I still do need advice about it though please. Any help that could be given is appreciated immensely.