The UA spec is a high threat/high damage spec for tanking while giving up only a portion of your survivability. It can work well with hodir hard IF you have the gear and the heals to be able to cover you through the Frozen Blows. One of the tricky aspects of the fight for the tank is remaining fairly mobile and maintaining threat over your DPS who should be getting buffed to very extreme proportions. I would say that if there is a real place for the UA spec to shine it would be during this encounter hard mode.
"If I'm doing a fight and I need more threat... I try harder. If I'm doing a fight and I need my taunts not to miss, then I wear hit." -Veneretio