I agree that the fluxfire is overpowered right now and I think that the upcoming changes are going to significantly help as well. With supercharge only lasting one round, the one shot mechanic becomes much easier to counter (with reflect, kick, liftoff, burrow, etc.).
Also, if you are tired of getting blasted by this guy, start running a S/S Silver Dragonhawk. It's a CRAZY fast dragon with flamethrower/conflag that eats the fluxfire for breakfast. It's also fast enough to outspeed basilisks and snowmen to prevent stun lock combos and to negate the flayer's advantage from kick and blitz.
I tried running a darkness team for the first time last night and ended up running into the fluxfire quite a bit. To handle it with that team, I simply popped the pandaren monk's staggered steps and it dropped the damage down to a very manageable 800 or so. Including the darkness induced stun and using staggered steps, my monk took care of the feline in 5 turns with around 400 hp to spare.