all u have to do is have at least 2 dragoons in your party and a bard and you can choose the last party member but it isbest if it's a summoner and yah just use the dragoons jump attack over and over and make sure the bard is equipped with a loki harp
Have dragoons be the muscle. Get some healers that are stronger against magic (i think mind is the stat you are looking at) so that they can heal the sick and withstand a few jolts. You are fairly high in the levels so I wouldn't worry about leveling more.
Also, leave the shield off the dragoons and opt for a second lance. he should be in the air whenever possible and will be hit less. If you have the money, there is a weapon shop that is still open that sells an upgrade lance. Expensive and you'll find better fairly shortly, but if that's what it takes then thats what it takes.
Finally, don't be afraid to come out swingin'. Your first round or two should net huge amounts of pain upon him. Then dedicate a healer and support your big hitters. If you need an extra edge, find out his weakness (scholar, libra spell, or gamefaqs) and leverage that as well.
I feel like a lot of people say this game is harder than most RPG's but I find it to be on par with most of the ones I've played (if not easier). Really, just try and try again. If you get burnt out, take a break, formulate a plan, stick with it.