I visit this site frequently (You can tell considering I wrote the guide ;) ) so I will probably answer any questions here.
At first, I tried the 13/32/26 tri-spec. This spec is really a good starter spec when your gear is less than flattering (We're talking in blues here). It balances everything out and gives you some much needed stats.
When your gear begins to look more and more towards what I have going right now (I'm currently sitting 4/5 T7.5 and pretty much epic'ed out atm.), 32/39 will begin to outshine.
Rotation for both specs are the following:
PS > IT > HB > BS > BS > DC dump (Or Gargoyle if at 100)
Lately however, with the 32/39 spec, I've been doing things a bit differently. Seeing how Icy Touch is really a damaging attack in this and your ice damage really is a big thing, I've been playing with this rotation and have seen some scary numbers: (5000+ dps on Instructor Rav. Don't ask me why, but he's the guy I do the most damage on, not Patchwerk.)
PS > IT > HB > BS > BS > DC dump (Or Gargoyle)
Followed by
PS > IT > HB > IT > IT > DC dump
The point is with a 32/39 spec that BS turns your blood runes into death runes. With that in mind, I replace BS, which is a weapon damage skill (And two fast weapons are what are really required to make the spec shine.) and use IT, which is a pure AP factor which usually will hit a LOT harder.
Desecration in itself is not as bad as people think. It's a 5% increase to your damage. The problem, however, is any fight that you are bound to move, you are going to lose out on the buff. Also, it's graphic is rather annoying and covers up key detail. I remember one wipe in particular where my GM couldn't see the poisons Grobbulus drops at his feet which caused him to stand in there a lot longer than he should of and strained our healers a bit too much.
It's a highly circumstancial ability that can at the most have 3 points in the skill, equating to a 60% chance of it proc'ing. I just find I could just max out Necrosis for it's full potential and just put one point in On a Pale Horse (Which is not a dps increase btw, just no where else really to put the point and 20% desecration didn't seem like there was a point). Some people take it, others don't. Really, it's entirely up to the player and how comfortable he feels when he's got to move around and recast Plague Strike just to get the extra damage.
For dual wielding, Howling Blast is key to the rotation. Our rotations will change very quickly to maximize the amount of HBs. Also, you may very well see 13/32/26 spec potentially just die because the need to change your blood runes to death runes will be paramount to a sucessful dps rotation.
AoE Wise, for both dual wield and two hander, this just gave a HUGE boost to AoE tanking as frost. My guess is that you're going to see a lot more AoE tanks like the frost spec as you could blast off three Howling Blasts for a ton of AoE threat.
And as for Obliterate vs HB? On AoE targets, HB will be your tool to replace. However, with the Sigil of Awareness plus the damage that Obliterate can dish out, it will probably never replace Obliterate for two handers. With a dual wield build, I find myself hardly ever using Obliterate as an Icy Touch + Plague Strike after using Rime seems to be the better damage output. This is untrue when it comes to a two hander where Obliterate usually shines. So no, I don't think Obliterate will be removed from two handed rotations just yet. And I think you do have an idea about HB critting more often, but, I'd still only use HB when Rime proc'ed and use Obliterate. But who knows, hell, I was surprised when they said they'd do that because that really shoves unholy in the face when it comes to AoE tanking as it now pretty much solidifies Frost as a great tank for both single target and AoE target. But tanking ain't my real forté so I will not touch that and let the tanks debate it.
Pretty much what he said is right. AoE threat's going to shoot up so much for Frost Tanks that it may potentially cripple Unholy. That's still left for the judges to see but I have a funny feeling you'll see a lot more Frost tanks now.
I'm usually at the top of the DPS meters on most fights (When my ghoul and gargoyle decide not to be idiots and die at the start of the fight...). It'll be interesting to change the rotation to something new...and as I can see now by loading WoW, 3.0.8 STILL hasn't been released, which is utter balls. ><

