Haha, you're lucky you get 33k per quest Hachoo ... Good ole RAF :-P ... you will only end up at level 58.5 if you don't have RAF on the characters (or at least I did, and i did ALL quests).

I've got 4 DK's at the moment (1 completed all of the quests just to see how I enjoy the class); at this point, it looks I'll be dropping 3 of my shaman (at least until dps gets fixed post 70) and 1 of my pallys in my 10 box team in order to fit in the DKs.

I've gone full Unholy for all 4 of the DKs (@ level 58 their Anti-Magic Zone protects me aganist 12,000 magic damage (75% redux), all of the AMZ's are on a rotation too, so I can keep a 12,000 damage magic shield up 100% of the time (theres nothing pre-Wotlk that can break through 4 rounds of it). Since it scales up with gear, I can imagine having an AMZ of 15,000-18,000 easily by the time I get to 70 (this should make for easy TBC farming, IMO). The gargolye is a sweet dps tool as well... 4 gargoyles that each hit for around 1600 (6400 total nature damage) on a click (3 min cooldown though); and I haven't gotten unholy Blight yet, but I imagine that I'll be spamming the crap out of that... as between the 4 characters its a 3800 AOE dmg DoT. Combine this with 4 ghouls, and you're really having fun.

It's a bit early to tell how the DK's will shape out end game. I've looked at some parses and DKs are constantly in the top 8-18 of the damage dealers on any given raid (I've rarely seen them break top eight), but it looks like in end-game wotlk, Hunters/Rogues/Retadins are coming out on top of the meters, followed by Mages, some arms warriors, locks, followed by DKs (Dks have been all over the charts), and at the bottom of the slope there appear to be shaman (I have had a hard time finding consistant data on elemental shaman builds end-game though, so feel free to dispute this; from what I have found, the shaman are in the bottom tier of damage dealers, end-game at this point). I'm sure things will be able to plow through an 80,000 damage - Anti-magic damage shield no time, but for now, I'm having a blast with these toons. Im going use my full holy priest along side the toons to help with damage control.

Edit: I should point out that in my post, I meant to say that there are no creatures (outside of raid bosses) that can break through the Anti-Magic Zone rotation. I'll run some more tests this weekend, but at this poitn im fairly confident that with a 4-DK rotation, you could easily TANK through Talon King Iksis, even when he nukes (although you wont be able to damage him, thanks to his shield), but for a laugh, I will try and fight him while taking each Arcane Explosion with my characters under the effects of the Anti-Magic Zone.