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.

No, I did not the toggle the ICC buff. You just need to head over to the warlock forum and see that they are hitting 19k (without ICC buff) with Best-in-slot reforged. For the DK, I just took your numbers for the Frost_2h_DK as he has the same equip and talents and that says 13.3k. So I was just surprised to see those huge differences in the sim, when they are a lot smaller in the real world.

For diagnosing high or low dps, it's really helpful for you to pick a fight in WoL, run the sim with the same fight duration, and see what is different -- are abilities hitting harder or softer? Are you using some abilities more often than others? Are the uptimes of various buffs (especially dark transformation, runic corruption, and shadow infusion) similar? Is the rotation you used in the fight similar to the rotation the sim is using?

There definitely are some places it's off, but it should be converging for level 80 pretty quickly -- at least, Unholy should be. I'm not sure about the state of frost or its accuracy.

r5307 build directly from svn: ./simc ../profiles/Death_Knight_401_Frost_2h.simc max_time=180 iterations=50000 target_level=83
only yields 10835 dps.
Comparing SIMC vs Weblog (corrected for ICC Buff)

Melee 2600 vs 2600 // crit % are fine
FrostStrike hits for 5109 vs 9303 // crit% are ok
Obliterate hits for 11177 vs 10000 // 30 vs 50% crit
Howling Blast hits for 6000 vs 3800 // crit % are ok

What should make us really suspicious here are the low froststrike numbers, the rest is likely to be just variance. I double checked with yesterdays full ICC run and he always hits for ~10k (without ICC buff), so it seems there is something odd. Also the crit percentage of obliterate is 20% lower than it should be. Anyone wanna take a look in the sources?

p.s. "maybe" froststrike is currently double dipping into the ICC Buff on live?
or FrostMastery is not handled correctly yet? that could explain the huge gap between the numbers

Unless your gear is the exact same as the profile used, please generate your own profile from the armory or wowhead. You can also toggle the ICC buff on to prevent math errors. Also, please include patch=4.0.1 in the command line, so that the correct coefficients, base damage, multipliers, etc are used.

There was a change to mastery in r5307, so it could possibly have broken mastery, but that wouldn't account for a near double difference in the damage of frost strike.

In regards to the crit rate of obliterate we didn't have KM affecting it, which I have fixed in r5311.

[e] Mastery was broken and is now fixed in r5312, bringing the 2H Frost DK up to 12430 dps, no ICC buff.

Thanks for the fix zimeron, we are getting closer:
16,3 simmed (icc on) vs 17.7k live ( equip is the same but just herkuml instead of the deathwhisper trinket)
Once again, taking a look at the damage sources of SIM vs Weblog ( Saurfang HC 25)
Obliterate: 14.5k vs 13.7 k
Frost Strike: 9.5k vs 12.5k
So it seems as FS is still not implemented as on live. Going to ask my friend to do some test on froststrike doubledipping while copying a DK myself to the PTR. Maybe someone else can add some data?

Edit: no ICC Buff on the PTR *sigh*

Not DK specific, but there is also the 8% magical damage bonus. I'm comparing to my sim's code, I don't see anything else.

All the standard buffs/debuffs have been updated, so that's included as well.

Taking a look at other parses on WOL, you see, e.g., against General Zarithrian, rankings where people are hitting for 9.5k without the ICC buff.(we can assume that they also have BiS gear) so it does not look like Frost Strike is double dipping.
Another idea:
Could it be that the server has stealthbuffed the froststrike and the client / it's tooltip / simcraft do not yet know about that?
On live it says 110% damage, but, e.g., latest PTR Build tooltip says 125%. Can someone run some tests with different equipped FrostDKs on live, e.g., using different weapons and then see whether it really scales with 110% of weapon damage? Don't have one myself on live right now..

While looking at the issue, I have seen something strange on Live. When I'm not frost spec, the tool tips on FS is 110% weapon damage. But whenever I spec for it, it transform to 121% damage, just by selecting frost main tree without any talent.
That means there is a 10% bonus somewhere.
Blood of the North - Spell - World of Warcraft
Effect #2 Apply Aura: Add Modifier - % Value: 10

That would be why yours and my sim have a low FS compared to WoL.