When I did it (at level 53) it was a piece of cake, but that's because of who I was with.

I was with a 71PLD/WAR, a 70+ WHM, a 61PLD/WHM (he subbed WHM since he knew he wouldn't be tanking so he could Sneak/Invis himself on the way), a 61SAM/WAR, and a 60+ BLM. The hardest part, like Sin said, is getting there. If you have someone that is 68+, they will not need Sneak/Invis at all on the way there, and can open all the doors for you, which is something to consider. The part to be careful with on the way there is the part with the teleporters. Every time you teleport, Sneak/Invis wears, so you gotta be careful and reapply it after every teleport. On our first one, we kinda made a train of demons because one person must not have gotten Sneak/Invis up in time and got aggroed. We took them all out without any problems, though, and continued on to the Throne Room.

I think my favorite part of the fight was the fact that I wasn't completely useless in it. ^^
But one observation: BLM is very important for the first (melee-resistant) form, and WHM is very important for second (AoE-happy) form.