I always get his health to 70%, and than no matter how many times I hit him, it never seems to go down!
the pets I use are:
raven:
119 strength, intelligence, agility and dexterity.
127 magic and physical damage.
can do slash

mystic:
204 strength
128 intelligence
120 dexterity
122 agility
212 physical damage and 64 magic
can do slash

lilly:
136 across the board, 203 physical damage, 68 magic.
can do beam.

I got lilly and raven using slash to do damage over time, and lilly to heal the team. I thought it was a good stradagy, but like I said, I can't seem to get fire eye's health down past 70. any tips?

I had the same problems and trained a new team.

My lead is Ephona who is element Earth. I used all her points on health, stat and proficiency.
Her Backups I used their stat points on Health then their proficiency points on Intelligence in the Light element.

I did this because Light is magical damage which is higher effective against Fire Eyes's physical, on top of healing party members a small amount each turn. The down side is that Fire Eyes's attacks are also highly effective against them
Earth is a physical element and takes less damage from Fire Eyes's physical attacks. Beyond that, the Earth element attack can draw it where he will only attack that one sylesti which saves your magic users from being damaged as much.

Pay attention to Fire Eyes's effects. When he gets Heat of the Moment, make sure your lead pet blocks. Blocking prevents the critical hit that it would otherwise inflict and you can still attack with your other two pets

sooooo.... 3 attempts ago all I was able to was to bring him down to 45%.
party changed, then 25%
now, with the same party but a bit changed tactics to 8%

:-) lets see...


update:

3 percent, gosh!!!

...and a new update, a couple of minutes later: YAAAAY! FINALLY! DOWN DOWN DOWN!

it was the same party. there is some luck part of the game as you have those 25% chances for special abilities to work (like bruses and healing), so I needed a turn where the luck was a tad bit more on my side. with a better party pure luck should be not what decides the battle but I did not want to wait until I captured 3 new lvl25 pets and resetting proficiency points to test around with the current party was a bit too expensive for an arena fight, so I just tried on with what I had now in my stable.

down, down down!!

party set: 3 tanks, one air, one light, one dark. all, really ALL points set on health. any skill points they have are from euipment only. epic and legendary, as usual. lots of switching the pets around, blocking in time (blocked all pets on both heat rounds this time, I had bad luck last time when I tried to block only the middle pet on the first round, he hit other pets on the first round too).