I found that Aeroga doesn't help much. The way I found that works for me is right before he uses sin harvest, or heartless angel, or whatever it is, he'll hit you with a two or three hit combo, then teleport off to the farthest corner. Go whack him up right as he teleports. If you can't make it, be sure you have all elxiers equipped, run away and hit it before his completes the attack so it has enough time to work.