"Im Chad "Brosef" Huntington. And I despise looking at fat people. So I came up with Bro90X. The only BROgram that will MURDER you into shape."
"Energy drinks? Those are full of empty calories, fatty calories, LOSER CALORIES; WATER?! That'll go straight to your hate handles!"
"But Chad I cant do thirty pull ups", TAKE THE CURLY FRIES OUT OF YOU MOUTH AND TRY HIPPO!"
Just imagine how much better you'd do if you DID use Unholy Presence.
Just because you are beating someone in dps doesn't mean that their spec or setup is worse than yours-- it just means you're a better player.
With your current setup, even though you are beating people in dps, you are not playing your character to your full potential.
I haven't lost in dps to another DK in months as an Unholy Presence DW Frost DK, and I typically stomp Frost Presence DKs. It's too subjective to mean anything.
You may not be good at keeping up with the faster pace of UH pres, which may be why you're seeing a dps drop. It also has a different priority than Frost pres dps, so you should make sure you're using the correct priority rotation.
If you can't do more dps in unholy presence then you're doing something wrong.
Unholy is better on single targets, this is a fact, it's not up for debate.
Some logs would be enlightening.