I got addicted to this game earlier this week after neglecting it for almost 2 years.
The reason I stopped playing it was the side quest to get the vampire class. You had to kill 6 dragons to get access to the dungeon that it's in and they were all super tough.
I went from level 65 to level 68 (each level requiring about 50,000 exp to get to and each battle giving around 1000-2000 exp) and optimizing my party's abilities and equipment, I was able to take down most of the dragons with much ease.
I say most because one of them was a real bitch. I spent about half of the battle trying to revive Agnes (my spirit master/white mage) with only Tiz alive (my templar/backup white mage who is an absolute tank) to get my team back on it's feet.
btw I actually got Tiz to get a pretty crazy amount of physical defense. That dragon was only doing 1 point of damage to him with each attack.
Here's my party and their classes.
Edea - Swordmaster/ Summoner
Tiz- Templar/ White mage with low level spells
Agnes - Spiritmaster/ White mage with high level spells
Ringabel - Spell Fencer/ Freelancer (just for the examine ability)