I suspect that mobs in Ulduar have more armor than Naxx/Maly did. I NEVER do as much damage in Ulduar as I did in Naxx 25. Anyone know if this is true?
I've noticed conversely, that on Emalon 25 man, I do quite a bit of damage still, usually around 2k dps when main tanking.
I've noticed a bit of a drop too, even with my same old Deep Wounds build and better gear. I too only have very slightly less hit and expertise than I did before stacking stamina.