While that might be true, I think you're hugely over exaggerating the value of that timed DS heal/shield. While I understand the principle, in reality you're playing the sponge 'role' if you're going to use your DS like that. If you are using them actively rather than reactively you're preventing damage, rather than healing it up.

I've healed before and I'll tell you, seeing huge spikes come in that the tank himself helps to heal back up is much more prone to freak out a healer than taking a little extra damage in a whole. YMMV of course, but I think I'm going to stick with my avoidance > mastery > threat for now. I might try out full mastery, but honestly reforging to threat stats is something I don't think I'll ever do.

I'm reading through the glyphs seeing that DRW is Mandatory for a 50% threat increase, might just be me but in heroics 5-mans and raids I haven't even had anyone creep close to my threat. Use a few Rune Strikes and you're golden!
EDIT: Though then again sod 15% run speed get rid of Bone Shield want run speed just go on UH pres :P

With AoE being what it is now, healers are leaving HP a little lower as topping them is a strain on mana (or so I find).
To help wouldn't it be more benificial to have Rune Tap as the major instead of the (imo) pointless threat?

Healing 5% hp with current health pools is 20k per person which will leave a lot less strain on healers.

5% of ~110k is not 20k. I do tend to glyph Rune Tap for some fights like Chimaeron and Conclave (there are more!) but don't overestimate how much healing it does.

I've updated OP to demote glyph of DRW, as I agree we don't really need more threat. I don't think there's a compelling argument for any other glyph to be its mandatory alternative though. Thus the recommended spec now leaves that glyph slot empty. Rune Tap is fairly compelling, though I think most endgame raiding tanks will swap it in as they see fit.

For gems/enchants/gearing: whilst I think the general arguments are now in favour of mastery or avoidance instead of pure-stamina, it's not conclusive yet so I have left that referred to as an ongoing discussion.

For Lichborne, I don't think the OP really needs to elaborate as instead I've linked to the very detailed discussions we've had elsewhere.

I think we should add a few recommended addons to OP, though. I can't play without Doc Debug Runes and Blood Shield Tracker, for example. I'd welcome any discussion in a constructive EJ-fashion on endgame raid tanking addons; or via PM.

Re: your point #3, while Death Strike absolutely heals off the non-physical damage that avoidance doesn't affect, Mastery would also have no effect, as Blood Shield is physical only. You'd get bigger shields on any non-magical portion of the damage intake, but avoidance would also impact that fraction, so while I wouldn't call it a wash necessarily, I also don't see an obvious reason to aggressively pursue Mastery as magic damage increases.


Unless I'm missing something entirely obvious?

The larger shield you get from healing the magic damage reduces subsequent physical damage.

To make the scenario simple, call it a dragon that sometimes breathes fire on you. The simulation results show that, if you ignore the breath entirely, you will take 1% less damage by increasing your Mastery than you would by increasing your Avoidance by an equivalent amount of Rating.

Once you add the breath into the equation, however, the amount of damage that the extra Mastery reduces goes up because for the Death Strike(s) that include the fire damage, your subsequent Blood Shields will be larger than if they included only the melee attacks at that time. The amount of damage that the extra avoidance reduces, however, remains the same.

Put another way, at 120% Mastery you are removing 34.8% of each breath's worth of damage from your total physical damage taken when you get hit by it. Also consider the old Stamina vs Avoidance argument in which the ultimate trump card was that you can't dodge a fireball. Avoidance has no effect on your total damage taken when magic damage is a factor. Mastery, however, does. In principle alone it should be superior.

The thing that annoys me about the DK mastery is it requires your Death Strikes to actually connect which in turn means you want some healthy amount of expertise and hit. Avoidance stackers can largely ignore those stats because landing a DS at the right time is much less important to them than mastery stackers. Even with 26 expertise and 7% hit I still run into situations where I get parried 3 or 4 times in a row and lose a huge Blood Shield chance (Cho'gall connecting twice in a row with Worship buffs up for example).

Gearing for avoidance also plays nicely with Dancing Rune Weapon since that ability gets better the more you have and that gearing method is also less affected by bad play, below-average RE procs etc because that survival is largely passive.

The advantage mastery has is that you can use DS as form of mini cooldowns better than if you geared for avoidance since you can save your runes for that occasion (see any boss that doesn't hit hard most of the time but has periods where he gets a damage buff or something) and obviously any bosses with (burst) magical damage.

Personally I am running mastery/stamina heavy because I like DSing more reactively and the stamina helps with Rune Tap, Death Pact, min DS heals, (glyphed!) AMS and indirectely with Lichborne (you can use it when you are lower on health since LB tends you cap your health most of the time anyway). The fact that I also do a big amount of interrupting in our 10 man raids also mitigates the blow of having more hit than I'd otherwise want just for keeping aggro (which is probably around 0% <_<).
I am going to try full avoidance gemming next week and see how that works out with the Rune of SS and exp/hit reforged away completely.

I don't think you take into account hit/expertise requirement of mastery - most mastery people keep capped hit/expertise while avoidance people reforge it all into avoidance. So to make it more correct you should substract at least half the rating needed to cap hit/expertise from mastery or add those values to avoidance.

Also I think it will be better to simulate increases in both stats at once since increase in avoidance should (theoretically) decrease value of mastery. I'd do something like this - add X to avoidance, add 2X to mastery, sim; add X to mastery, add 2X to avoidance, sim. Of course this x2 multiplier came out of nowhere but I think this way it should be more close to how our ratings gonna increase.

While you can't dodge a fireball, and I'm in general agreement with the guaranteed next-hit reduction vs avoidance chance argument, it doesn't sit well for me to say that in a mixed environment, avoidance has NO effect. Unfortunately, this puts me in the unenviable position of arguing against a simulation. Looking at the numbers, however, and taking into account the 100% physical aspect, I do have to agree, mastery outweighs avoidance, at least until we run into something silly and unlikely like a Hydross-style elemental damage melee boss.

This doesn't look like a Wrath-style "stack at all costs" scenario, however. Do you have numbers for/against a generalised balanced gemming/enchanting approach, but getting Mastery wherever you see a yellow slot/available enchant? That would seem the best route, especially in a low tier where we're not continually flirting with the DR cap, as we were last expansion, but as I said, I hate arguing with a machine, because it's normally right.

On a 1:1 basis I'd agree but Mastery needs hit/expertise to function at it's maximum potential. I've tried gearing each way (mastery w/hit and expertise AND avoidance) and I found that avoidance seemed to work better for raids (some fights seem to favor it). I was unable to cap hit and expertise without going out of my way (gemming/enchanting) and that just didn't seem logical to me. Maybe once I get in heroic raid gear it will be easier to reach the caps but it was far easier to reforge to avoidance and not worry about hit and expertise with current gear at the start of Cata.

Thanks to the upgrades I made, I can now run significantly larger sample sizes when I make use of my work machine, so, these results are from the average of 500 eight minute fights each. I'm lazy, so I used the default stats other than Hit and Expertise. There are two passes - One with Hit and Expertise soft cap, and one with 0 Hit and 0 Expertise.

	Average Damage Taken
At Cap	4,740,900
At Zero	4,789,827
Increase	1.03%

It looks like your hypothesis is wrong. As respectfully as possible, if you want to dispute this further, download BloodSim, plug numbers, and run the results yourself. That's why I wrote it and made it public. Anecdotes are adorable, but have no value. I'm open to being proven wrong, but I'm not going to do all the work for you.