I have been searching the data base for half an hour now trying to find my answer, but I am unable to. Can some one please help me out. I keep reading about UH doing 6k+DPS. Is there a good guide out there that covers this explicitly? I only have a 4.8k gs but i have enchanted and gemmed my gear to the best of my ability and only do 4k dps. I know i'm not the best but i am trying to improve. Mostly 5 mans and some raids when they will let me in. If you only want to flame me, please don't bother. I am not the best yet i.e. thats why im here.
You haven't said what your doing 4k dps on thus there are no facts in your statement.
IE your not going to do 6k dps with mediocre gear in a heroic as unholy. Thats not the way the abilities or spec works. Frost and Unholy both have a significant amount of "wind up" time.
Elitist Jerks covers everything you need to know. If you have any questions, ask there. There are already dozens of threads about unholy dps, you just got to look, answers are there.
UH DK's get better the longer the fight goes on. With a GS of 6035 (I don't rate GS but if this helps you understand what level of gear I'm using then so be it) I can hit 10-12k on Saurfang but it drops to about 8 on a fight like Deathwhisper etc. It really depends on the encounter.
If you're talking aboiut heroics then forget it, things don't live long enough. I lol'd when some idiot troll'd at me for only hitting 6k on a 5 man boss that died in 19 seconds. Massive numbers just don't happen so don't worry.
If you're talking about a raid then you may be having a slight issue as you should be close to about 6k in your gear level (Depending on boss obviously).
Whats your rotation? Also post your stats (Str, Crit, HR, ARP etc etc etc) and I'll see if I can identify the problem for you. It could be something as simple as the wrong rotation which can be fixed easily. Latency also effects DK DPS, which I found in the past when my computer sucked.