Suzaku, this is a very good guide, and I almost gave up fighting him in the first place until I thought of your tips. My light dragon is only level 81 and just beat Don Giuvanni.
As a mage, I can only point out that all the tips here would work better for sheep than dragon. In your video, you were able to lure him pretty well with Cleaving Terra and Mana Storm. You had multiple attack skills, and Terra itself has a HUGE range.
My mage has only a level 10 Arrow Rush and level 1 Arrow of Light. >_> But the info about the map layout really helped. I was also able to attack him from the very TOP LEFT corner (there's also a rift there between the two platforms) and it works even when you've switched positions. In my experience, Don will eventually move to or close enough to EITHER one of these spots so that a ranged class can stay from a distance and attack him. If you add to your guide the bit about the top left, that might be helpful to others too. Um.. you probably know which part I'm talking about? If not, here's a screenshot... and where I'm standing, he would be standing on the platform right opposite me with that huge gap between us. It's another spot that works well for a mage with Arrow Rush, since apparently the spell range is long enough to hit him from that distance.
Took almost an hour to kill the douche but I did ok thanks to this guide. ;o