At lv 80, Fei, Citan, and Rico should have way over 650 HP naturally. Otherwise, you can always pump up your HP, Def and EthDef using the drives. That'll take care of the defense part. Try to wear a Speed Ring S and have a Speed Shoes on each char.
Though there are uncountably many paths in life, the path to our destiny is the only one.
If you can manage three Speed Shoes (the third essentially requires the Trader Card or "lottery luck"; the second is simply the most expensive prize in the Battling Arena), and bring Fei, Citan, and Someone Else (really, with Fei and Citan, it doesn't matter), you should easily enough be able to slaughter Dragons with sheer force of awesomeness.
The Power Crisis certainly helps - Speed Shoes, Power Crisis, and either of his top two deathblows, basically make it so Fei can essentially solo dragons. The problem being, I don't like relying on low health like that. (Maybe it's just me.)
"As the good archmage often admonishes me, I ought not to let my mind wander, as it's too small to go off by itself." -Danilo Thann