I wasn't testing whether or not the modifiers were additive. None of them (at least for Plague Strike) logically should be, anyway. My test was simply to see if the strike worked the way an instant melee attack should-- tzenes was asking if blood presence modified both weapon damage and overall damage, and my assertion was that it did not. My hypothesis was that "weapon damage" in the tooltip means simply normalized weapon damage, and additionally my guess was that 2h weapon spec increased that damage value specifically, before other modifiers. Given the discrepancy in values with 2h weapon spec in Frost Presence, I can't be sure that's the case yet.

However, the point was that everything else worked as expected, within a tiny margin of error. Weapon damage is normalized, and the modifiers that affect it are multiplied after the ability's damage is calculated. This all might seem obvious, but it's worth getting it right for the spreadsheet and future calculations-- it's nice to know that we understand how it works. Blood Presence doesn't apply twice, nor should it, so that should answer tzenes' question.

Also, it wasn't just that the numbers with 2h spec without blood presence were lower than expected, they were exactly the same as without 2h spec, all other things equal. If it were additive with anything, as you're suggesting, we'd at least see a somewhat different number. Besides that, it performs as expected multiplicatively when Blood Presence is up. Something's fishy there, but I don't think that means any of those bonuses are adding.

Here's my current thought about additive versus multiplicative modifiers. Any talent or buff modifying a different "category" of damage should be multiplicative. 2h spec modifies weapon damage. Then, Outbreak modifies Plague Strike damage. Blood Presence, Blood Gorged, and Bloody Vengeance modify total physical or overall damage, and even though some of those cover similar "categories", we've seen that those are all multiplicative too. Really, there's nothing yet to suggest that any of these are additive.

My point with this test was to see how the melee strikes worked. Scourge Strike deals shadow damage, but zurm's blizz quote confirms it's a melee instant attack, and is subject to all the appropriate rules. I think we'll find it follows a similar formula, once it's working correctly again. I haven't touched spells yet-- Icy Touch is going to be different from a melee attack in that regard, though I'd guess the multipliers from talents, etc, would work similarly, and blues' numbers with death coil back that up.

I worked through the math and Death Strike theoretically always outpeforms Scourge Strike for TPS and outperforms Obliterate at 2 diseases with over 500 Normalized weapon damage. The equations used are :

W = Normalized Weapon Damage
D = # of Diseases

Death Strike threat = (W * 0.6 + 178.2) * (1 + D/2)
Obliterate Threat = (W + 217) + (108.5 * D)
Scourge Strike Threat = (W * 0.65 + 196.95) + (98.47 * D)

This is using the max ranks of each of the abilities with numbers pulled from MMO Champion. Note that this is without factoring armor reduction which would favor Scourge Strike and talents which might favor each of the three differently based on spec.

Since Death Strike threat essentially scales with W*D*Constant it will eventually outperform anything that scales as (W*Constant + D*Constant) given large enough values of W.

This seems to be the major limiting factor, but at high normalized weapon damages with 4x diseases the threat per use is around 50% more than with Obliterate. In a situation where even half of your healing from DS produces threat it still may outperform Obliterate. I imagine this will be more useful for threat in 5-mans and perhaps in 10-mans that you overgear and can sacrifice a healer for an extra DPS than in 25 mans.

Below are the graphs showing the behaviour with respect to weapon damage and diseases.

Death Strike Threat per Hit

[Edit: Typo fix and added link to charts]

From my understanding of command, it applies to any true pet (you need a petbar for it) of a hunter, warlock, or death knight. It's definitely worth testing, however, to be sure.

Ghoul Nerf: I think everyone saw that coming. No real problems there, as long as they realize that the only reason that DK's need a damage buff to compensate.

Chains of Ice: Ok change but then it should probably cost 10-20 RP instead of a F rune. It was only justifiably worth a precious F rune when it couldn't be dispelled - now that its power has gone down a lot, so should its cost.

Strangulate/Mind Freeze: Strangulate CD going up is ok I guess. Probably a little too good.

AMS: Probably needed as well, although the wording concerns me. "Icebound Fortitude to use often" means that it will have a shorter CD than AMS? Confusing. I guess this makes the 5 extra seconds of AMS for 15 second longer CD glyph potentially better. With a base duration of 5 seconds and a 15 second CD, the gylph was kinda meh but the longer the new CD of AMS the better the glyph is (since you are doubling the duration but only adding a flat 15 seconds to CD). Any longer than 30-40 seconds and it becomes a once_a_fight spell anyway so might as well glyph it for 5 extra seconds.

I have no idea what that last sentence means. DK fights tend to be a drawn out affair with our lowish damage going up against your damage (made likewise lowish by all our abilities).