In the first encounter, the Conclave of Wind, you must split your raid into three parts. There are three bosses on three different platforms. Your team must be able to move across the platforms in a coordinated way and react to what the bosses are doing. Movement of this kind can be very disorienting for a raid, so folks who aren't comfortable with the dance steps could have some trouble.
The second encounter is against Al'Akir. It's a three-phase fight and ends in three-dimensional space. Interestingly, Al'Akir combines the "fire wall" mechanic from Sartharion as well as the "fly around" mechanic from Malygos. Again, if you had trouble with those fights, you'll probably be challenged here also. That being said, Al'Akir is a pretty fun and engaging encounter.
Ready Check shares all the strategies and inside information you need to take your raiding to the next level. Be sure to look up our strategy guides to Cataclysm's 5-man instances, and for more healer-centric advice, visit Raid Rx.