Did it 3 times with a full alliance of 68+. One of our WHM was being a moron, got pissy and left so we only had one WHM but all tanks were NINs.
First he will use his special move and paralyze people. A lot. Second, the pops are a pain, have 2-4 melee and a mage dedicated to just dealing with them (Tonberrys and Hecteyes). His spells aren't too bad. Myself and another BLM alternated Stuns and only once out of 3 fights was there a point where we both couldn't Stun and that was because I mixed up the order ><. He will cast Fire IV, Firaga III and Flare.
A couple of other things I noticed but can't explain: Hate was all over the place sometimes. Even with the NIN tank doing everything he could it would oddy shift toward a mage. During the first fight I was on Stun duty so I wasn't nuking for a good 2 minutes or so. He cast a spell so I Stunned and then it was the other mage's turn. About 10 seconds later I cast Bliz 3 for ~400, got aggro and was toast. Even though I did nothing for a long time I suddenly got hate and I don't know why.
The other thing is he would resist, a lot. 75%+ of my spells would be resisted for only 25 damage and that's with AF gloves, all the +INT I can have at this level and the appropriate staff for the spell. It seemded like his resists would rotate. For example, I could hit for full or almost full damage on say Bliz 2 and 3 but then doing a Thudner 3 would get almost fully resisted. Then a little later same thing for Thunder 2 and 3 and Bliz would get reisisted. I don't know if it was coincidence or what.
Anyway, we won the first 2, got smoked the 3rd. A couple people left so the alliance didn't have very many mages and we got 2 pops, one of them being a Tonberry with an elemental.