We didn't make any changes in Blackwing Lair. We did alter the way the Nefarian reset works, but that's about it.
We have also since gone through all our data and verified that no changes were made to any mobs hitpoints or damage output.
Please note, we did make significant improvements to performance in Blackwing Lair. We added a performance slider to your graphics options. Also, we made some changes to the way the game reacts to UI modifications which caused a huge reduction in lag for many people. When players complained about lag months ago, we made it a priority to work on the issue. We've also been warning people for quite some time now that there are some pretty inefficient UI mods out there. We'll continue to work with the mod community to help them improve their performance.