How is the ghoul being simmed? I ran DW frost sim, one with horn of winter as last priority, one without. The DPS was higher without horn of winter, and here are the differentials by total damage, which show the increase in damage done without using HoW (except for Oblit, described below):

Army of the Dead | 212
BloodPlague | 325552
BloodStrike | 373200
FrostFever | 192848
FrostStrike | 4311040
Ghoul | 3573456
HowlingBlast | 6013696
Melee | 124352
Obliterate | -1446528
PlagueStrike | 93380

These results I generally expected, as the minimal runic power gained by horn is offset by the fact that you are stuck in the GCD, and if runes come off cooldown before the GCD is over then you are wasting that resource. The lower Oblit damage is due to more KM procs being used by frost strike when capped with runic power.

However I was surprised by the increase in ghoul damage. The only way the ghoul could be doing more damage would be if it were getting called more frequently. I then ran a sim with no strikes whatsoever, and ghoul damage actually doubled over the first sim. It seems like the ghoul is only getting called when there are no other active priorities, which would explain why using HoW as a last priority would decrease ghoul usage. If this is the case, I would create an explicit priority for summoning the ghoul so that we can figure out it is supposed to go.

I also have similar strange issues, but...I cannot even seem to reproduce your 40%. With 0 diseases up, no tier 10 on (10% multiplier, but does not double dip as tested but discovered later) and no glyph of Scourge Strike, no trinkets, no Ashen Verdict ring, runeforged my weapon to Sword Shattering so I have 0 procs....I am getting a tiny bit over 52%. Glyphed I am getting .63.

What it must be is Rage of Rivendare double dips and is additive with the Glyph of Scourge Strike.

Example (no glyph):
http://i530.photobucket.com/albums/d...210_151356.jpg

Glyphed: .36*(1+.3+.45) = .63
Unglyphed: .36*(1+.45) = .522

The buggy thing here:
With Ebon Plague up, it gets no bonus to the shadow damage. With Curse of the elements, it is at .668 (should be .6804). With Earth and Moon it is .71 (adding 8% on). All of these work as you would expect for normal abilities, but not Scourge Strike.

I have added some missing gems in the sim, but they might be some others missing. For information, the gem list is automatically extracted from Gems - Items - World of Warcraft. But there are some missing that I had to add manually.
I have also implemented the D&D bug that add 1 tick and by the way make some test and see that D&D crit are now 200% damage of the non crit, which was 150% before 4.0. I won't cross posting it in the Unholy threat but this confirm Consider's math regarding dw versus 2H.
ps: I have updated the OP to add some explanations regarding the new features of the sim since the old WotLK version.

There appears to be something slight off with the Sim and how it is handling hit currently. I threw together a DW unholy DK (5%) cap, and started reforging items. However, as I increased hit the dps continued to go up. I assume it was the spell hit cap (17% - we should be capped with 8% melee and 9% spell hit via talents) However, I continue to experience increases in DPS as I increased hit rating until I went from 1151 to 1219 at which point I lost 2 dps.

This was tested in BIS DW gear, with Lava Spine x2, using gylphed DnD in the rotation. Melee hit cap is 605 rating as DW, otherwise at 961 (8%)

I've run into a curious issue. @80 having reforged my haste to mastery, i've found that my Frost Strike hits are landing harder than my Obliterates. Is this true for 85? or is the scaling going to put obliterate back on top? Presently I'm in 264 gear, having reforged haste to Mastery for DW.

Bot are strike and are based on weapon damage. I don't have calculated the Mastery needed to have harder FS than OB. But if at your percentage of mastery your FS hit harder, there is no reason that it wouldn't at the level 85. The main issue is to maintain this high mastery due to the rating conversion changes at 85. Example: if you have 800 mastery rating at level 80, you will need 3124 to achieve the same mastery at level 85.

Just to confirm I'm not getting strange results, everyone else is simming strength higher than all other stats, including hit and expertise in dungeon blues at 85? Strength is simming out about 3x higher than the nearest secondary stat (either hit or expertise, depending on the sim run), for me.

Is it possible to add in some of the random items so the Sim knows how to handle them? Take the belt on my character for example, it comes from the Four Winds encounter and is amazing belt, however, the sim doesn't know that it can reforge the stats.

Unfortunately, in this current state it's not possible. I have made the item list with the item id as unique. This would take some work load to change that. I'll keep it in mind if I have nothing left to do on the sim, but I can't put it on top of the priority right now.
As workaround you can input manual stats for your character in the Stat Summary tab.

Are the cataclysm hc dungeon trinkets implemented in the sim yet? looks like to me that it's only counting the passive stasts and ignoring the procs, thanks.
edit: alright, thank you

I was just testing the sim and my biggest problem was that I just couldn't get the priority list right because there was so few choises there which lead to an unrealistic sim and twisted the EP values.
Maybe I missed something? Is there a way to add my own conditions to abilities like 'obliterate if 2x F AND 2x UH runes up' or 'FS if RP > 95' for example and if not are you planning to implement such feature?