For those that are having trouble with this the easiest way to beat this guy is with poison.
It took me 13 minutes and didn't hit him once.
Poison took care of everything.
Just make sure you have a sen/med/med, sen/sen/sen, and sab/sab/sab combo.
syn/syn/syn is useful but not required as you should be sen/sen/sen the whole time fight anyway except to cure or debuff/poison him.
When you get the watch just redo the fight using the same tactic with the watch equipped for the 5 star rating.