With each attempt we get better at reaching the Vael, the second boss inside Blackwing Lair. I think we were done with him 2 hours into the raid. The time includes one wipe on Razorgore (Raz) and a wipe Vael, which requires re-doing the Lower Blackrock Spire (LBRS) Fire Protection buff.
After Vael you deal with a five-dragon pull. Two of which have a fire AOE that will kill surrounding cloth-wears. We learned to steer those mosnters toward a wall so they only burn the tanks while we DPS them from behind.