The problem in your reasoning is that the argument that UP can use extra GCDs to weave in extra FS is sound, however the idea that the efficiency of the runes used in the extra free time is the same as the BP rotation is not.

If you use two diseases as UP, you'll probably run a rotation like (rotation as in rune usage, you'll probably break the scheme apart quite often):

PS IT OB BS BS - OB IT IT IT IT

in order to gain a decent amount of extra RP to actually have some extra FS to use.

A BP rotation not only has 15% stronger abilities, but it uses more damaging ones (namely 2 115% damage obliterate with 65%+ crit chance and 245% crit damage, compared to 4 puny IT).

Also, another very important factor when considering "burst" is that the UP rotation is certainly theorycally stronger on a full cycle. However, every time your dps window is smaller than that, such superiority is questionable. With 4-6 seconds of DPS exposure (speaking of Yogg, imagine the tentacles), the one extra strike you slap in may very well not be enough to catch up with the 15% damage loss, expecially if it's not a crit. Or if you're stuck on a point where you need to IT IT FS, while the BP guy would OB FS - he's gonna destroy you on damage.

I repeat, I played both rotations extensively. Despite having positively zero luck with the Sigil (which I would say it's pretty essential to frost dps) I managed to get a placement on the WMO top 20 for Frost on most bosses (at least till we switched to WoL). I don't want to diffuse the false idea that UP with the IT glyph and an IT oriented rotation isn't the first road you should explore as Frost, expecially if you do have the sigil. The consensus on that build is universal, and having used it extensively, I can testify it works and it's probably the first choice for Frost. What I'm saying here is that BP works too, and despite being different and definitely more difficult to use, it can produce very similar results (if not better at times) and with the changes incoming in the patch, and the much reduced impact of FS on our rotations, and the increased disease damage, UP is taking a strong hit and BP is getting a slight buff.

Just a curious question since we are aiming for OB 'n' stuff... Equip with ArP? Or more Str and Haste?

Anyone had the chance to test it out with enough ArP on equip?

I think we are going to have to wait until we have decided on competitive specs to work on statweights. Speaking of which, what we need to do now is find out specifically what the simulator / Spreadsheet creators need tested. I feel our only way to move forward is to get a working simulator to test builds, as we know the targeting dummy is useless for that.

Anyone disagree? If not we need to identify issues that are holding back the simulator / spreadsheet programmers and work on them.

Without a simulator a few conclusions can be drawn based on the current stat weighting for Frost. Currently ArP is below Str, but above Crit and Haste.

It seems OB and BS will become larger portions of our damage, as well as melee white swings which are all affected by ArP, naturally raising its value. Considering it already being better than Crit and Haste, I expect this gap to widen, however I don't see ArP ever being better than Str in any DW Frost build.

A spec I haven't seen posted that seems to be competitive is this: 10/54/7.
Best options seem to be using BP, FC/RI (RI seems to be far superior to FC, especially with the increase to 10%), and SoA (quick simulation showed a large (~175 dps) difference in favor of SoA, no comparison made with the new Sigil yet)

I've been running my simulations on a modified version of Kahorie's simulator (added information I could find in this thread such as sigils not being affected by the offhand penalty, runes only being consumed on main hand hits, razorice stacking up to 10%, and just now (aka after most of my testing) the 15% increase to disease damage and SotVH nerf). I also added the hit from Heroic Presence, which might affect gear choices but hopefully (likely) not much else. (Simulations with the BiS gear below ended up at around 6.9k dps, but keep in mind that most of the changes I made to the simulator lead to increased DPS (but more accurate) values compared to others' simulations, and as such you probably should run your own simulations on this if you want some numbers for comparison)

Original tests were done using my own DKs T7/T7.5 gear, but from further testing it seems to scale properly with T8 BiS gear as well.
BiS Gear stats used for those interested: Str: 1426, Agi: 245, Int: 46, Arm: 14291, Hit: 177, Crit: 752, Haste: 255, Arp: 160, Exp: 179, OH/MH: 178.9dps/2.7s, 4p T8
Yes, the hit is kinda low, but from EP calcs it actually doesn't seem to be that important (melee hit cap being a lot lower due to NoCS, and relatively few spells used)
LootRank listing (EP values derived from the T7 gear, being below spellhit cap. Above the spellhit cap the value of Hit falls to roughly 0.77 (or 77 with AP set as 100, but lootrank isn't a fan of big numbers :P). Note: Kahorie's calculations seemed a bit dodgy regarding weapon dps and weapon speed EPs, so I made some calculations of my own which halved the listed value of MH weapon dps, but makes more sense matematically, unless I missed something :P)

Priority used was: FF > BP > OB > BS > FS > Rime
With the T8 4P bonus moving BS above OB seemed to give a few (<10) DPS increase from a few short tests (2*24h simulations on each), and with proper estimation of free GCDs (taking into account Rime procs and such) it might be a worthwhile tactic for maximising DPS, but doesn't really seem worth the hassle in my opinion.

I also did some tests using Glyph of Disease instead of Glyph of Blood Strike, and it seems to be a DPS loss of about ~40, but still being better than using any other Glyph. (Note: The simulator's priority system doesn't take full advantage of this Glyph, and has to reapply disease with PS/IT fairly often even with it. In practice Glyph of Disease might actually be superior)

As for the Blood Strike Glyph, if you need to get Chillblains (did we get confirmation on whether this actually worked on bosses?) the best point to move seems to be UA (Though I once again wonder if this is something the simulator uses properly, and you might want to have both a dps and a survival cooldown for various bosses, in which case you probably want to move a point from Black Ice instead (didn't test that extensively though))

Hopefully this will help narrow down some of the questions in the OP and possibly help decide the spec to use in 3.2.

I agree with that.

I am also getting the best numbers with that build, seems to be the most efficient one and pretty neat in scaling with gear.
As I said before, you need Epidemic to get a smoother rotation which favors 2 diseases, OB and FS and just 2x BS for the death runes.

And as said before, Deep Frost will be the only solution to go. Blizzard is doing everything they can to block any hybrid possibility. So I think it would be fine to see some other test results from our dear fellow theorycrafters here.

Trying to picture the rotation, I have some doubts how that would work in practice.
The priority above should produce a rotation along the lines of:

IT - PS - OB - BS - BS - FS - FS
(10.5 seconds, disregarding spellhaste for IT (latency should account for at least that difference if not more), meaning you either have to wait 1 second to start the next line (U rune not ready yet), or use the time for HoW/Rime/Excess RP dumping (should be some after a few cycles, even without AMS soaking))

OB - OB - FS - OB - FS - FS
(Waiting out the 1 second means the last GCD ends at 19 seconds from start of rotation, using it for random abilites means 19.5 seconds)

Changing the last OB (that's the one that uses the Death Runes) to 2*BS would then add another 1.5 sec, meaning that IT would run out before being reapplied (you don't want this: Tundra Stalker on 6 ticks of FF gives you 0.9 of a full tick, giving you a DPS gain if you reapply it in the 0.3-2.99 seconds window (the closer to 2.99 the better obviously)).

--NOTE: The above parenthesis is a simplification and only really calculates the FF DoT with no regard to the cost, but it seems to make sense considering that rotationwise it's optimal to refresh after 2 rune refreshes, and the fact that you don't want to use any other ability without FF up anyway. The above math doesn't account for the increased IT damage either, which should be fairly large considering Glacier Rot, so I think it's fairly safe to say IT should be refreshed before it runs out but after the second last DoT tick.

Even if you did choose to wait out the 1 second window before the second line of the cycle, you'd only have 0.5 seconds to refresh your FF, which could easily be ruined by latency, as well as the fact that you lose more DoT time and stretch your rotation to an effective 20.5-21 sec per 2 rune refreshes. It also means you lose out on the window for HoW/Rime/extra RP dumping, unless you go back to OB on the death runes for those cycles where you need to do any of those (which I believe is likely to be most of your cycles anyway)

Changing FS GCDs to BS is not an option either for pure damage reasons (and you shouldn't have RP problems with this spec in BP)

Feel free to point any mistakes I may have made :P

Edit: So much wall of text

Depending on your build, you can delay the RP Dump (FS spam) till next rotation, like:

IT PS OB BS BS FS
then
OB OB FS OB FS FS

and back to the beginning.

Of course that requires Virulence

Blizzard is making every effort to ensure Deep Frost is the way to go, yet currently in PTR it's not the case, even with UB nerf. I ran some numbers from the sims of Kahorie's, and 0/17/54 always pull forward by a good 300 - 400 dps of the same gear level. I'm trying to tweak deep frost to get better numbers but no luck so far.

Err, read it as using the Death Runes for BS, as had been suggested by some posts :P

The problem with that is you'd have a very small window for FF refresh, it seems to be more efficient to add that FS before the second rune refresh (unless I'm mistaken your rotation will be slightly shorter putting that 2nd FS there as well).

For the glyphed Pestilence, my plan was to use the first one instead of the first or second BS (depending on when your FF is going to tick) and it should be fine, it's a slight dps loss but makes the rotation a lot simpler. I made the simulator do this, but due to the delay before the third OB in the second rune refresh the blood rune didn't refresh on time and it went back to using IT-PS to refresh it (which btw I think is preferable to PS-IT, you lose the Glacier Rot bonus on the first IT but gain the TS buff on PS+BP, as well as being able to apply it while running in). Might be able to figure out some other way to set up the priority to make it do this properly.

Edit: In an effort to make this post slightly less useless, I ran a simulation with 200 extra Strength but no useful Sigil (Arthritic Binding, for the record) to simulate 100% uptime on the new Sigil, it turned out to be roughly 60 dps worse than SoA (just a quick 24h Sim, but the difference seems big enough anyway).