Fireblight Ganon is more of a close range fighter than Ganon's other iterations, preferring to swing with his sword than fire projectiles. The best way to take Fireblight Ganon down is to get up in his face and dodge or parry his moves, then Flurry Attacking him to finish him off.
Fireblight Ganon can be a challenging boss for some in The Legend Of Zelda: Breath Of The Wild. His attacks might be slower than other creatures you've faced, but when they connect you'll feel it. 