I'm assuming this is about retail WotLK, which is fun and all, but my comments were about a potential WotLK Classic, since that's what this thread is about. This assumes 3.3.5 talents all the way from Naxx to RS, in which case, Blood Dps is never a thing. It's always weaker than Frost, even with 100% Arp.
And no, Unholy only beats Frost on ST when you get Shadowmourne, assuming equal gear and skill. Getting Shadowmourne is first of all very time consuming, and there's still no guarantee you will get it over a any of the other Plate Dps...
As for the Tank specs, why exactly would you want to be Unholy for Sindragosa? Sure, UH has amazing magic dmg reduction, but Sindragosa (HC) Frost Breaths hit nowhere hard enough to justify losing all the good stuff from Blood to get Bone Shield and AMZ (the only Tank talents deeper than row 1 of the UH tree). Even Private servers where the bosses are buffed to do 50%+ more dmg than what they did in retail, don't run UH tanks for this.'
The only boss in WotLK that does enough magic dmg to the Tank to justify building a whole new spec for it, is Sartharion 3D while he has the drake buffs, but if they go with non-buffed retail values, any Tank can faceroll that without issue aswell.
Why though. Any Plate/Hunter can run away and pingpong taunt it like people have always done against any boss post enrage. Not like the pet won't be oneshot instantly.
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Please tell me about this amazing utility that BM Hunters have exclusive access to. With all the Hunter utility talents being located in the Survival tree and all that jazz
There's no reason whatsoever to bring a Frost Tank to LK over a Blood Tank. The Frost spec has ONE single Tank talent in the tree excluding the stuff in row 1/2 that will already be picked up by a regular Blood Tank...