Protection, tier 8 2set VS seal of command

I'm currently running seal of command for dungeons and aoe threat/DPS, which there is a lot of in Ulduar. The tier 8 2set gives 10% dmg done to seal of vengeance/corruption and righteousness. Does anyone know if the 2 set makes righteousness more dmg/threat than command for aoe? Also is it worth speccing 5 points into "Seals of the Pure" for 15% more seal damage?

I'm thinking 2set bonus from tier 7 and 8 for a massive speed dungeon set. 10% hotr + 10% seal of righteousness. If seal of command is still more damage then might just have a 'tierless' build with just better stats.