I'm with most in the belief that the Pharos is the true final dungeon. I had a pretty easy time through it but then again I completed most of the Clan Hunts and got all the Espers. My party was average level 65 when I beat it the first time. I would guess the dungeon required a minimum lv 40+ party to beat.

I really liked the Garbranth battle though. The final boss' first few forms were easy but I laughed during the Undying cause its completely reminiscent of the final boss fight in Vagrant Story.