Done BWD today as 3, only tricky part was chimaeron as he liked to gib the dps with slimes (we run without a healer) and maloriak because we released every add at once and I had to tank all 18, fun 748k vengeance though. My 2 dps died at the start of nef and I ended up soloing him through p2 and p3 from 100% as a prot paladin, left 2 adds on the platforms just spamming blastwave as the damage was kinda insignifcant. Overall not very hard.
Honestly, only the older raids which have a chance at dropping mounts would be appealing, primarily Firelands and Dragon Soul. I'll see about getting a 10-man group together later today and having at both of them!
Arthas posed no problem for my group of 4 last night, so a group of L90s should have little problem with Ragnaros and Deathwing.