I never hate the Burn debuff so much before more than Poison,
But when Burn debuff can stack up over 1000+ dmg while DEF count only cap at 999, a dragged fight with this boss is just not winnable at all,
I just hope the DEV would capped the DEBUFF or increase the DEF count or even reduce this particular boss HP,
Killing the summons first the furthest I can get the HP drop to 19K while targetted the boss only able to go 6K
Unfortunately this is just a case where you have a bad enemy matchup for your build. Fire isn't necessarily a big deal, but you weren't killing the summoned monsters fast enough so they just started multiplying and stacking that burn damage on you.
These fights where something is summoning other monsters basically boils down to: Can you eliminate the summons quickly enough to give you a turn to deal damage to the summoner? If not, you're in for an uphill battle.
