Simcraft says that my ~272 destro warlock should be at 18 k and that my friend's best-in-slot DK should hit 13.3. But usually he is in the same area, only 1-2k dps behind in tank-n-spank as in Saurfang HC25
When you're simming both of these are you toggling the ICC buff? If not, then the warlock is simming to high (23.4k) and the DK is still a bit low (17.3k). If you are able to get a log from a DK, please include the profile, with reforges, and if possible the rotation. The rotation isn't as important as the profile, as with the profile we can at least see if the abilities are hitting for the same, etc.