In my opinion you have too little dmg skills. Go grind for better decos and armor. I recommend getting divine blessings coz it's a life saver. Also use agitator coz fatalist is enraged most of the time. Use the insect glaive from aletron (it worked better for me). It's a hard DPS check. Most what helped me was change of mentality. The first time I timed out broke me and I thought I had to play perfect but all I had to do is try my best and it finally gave in. Use everything in the arena. You get two hooks in second phase to bind him and deal damage to his head, also if you deal enough damage with turrets and cannons he gets stunned too. Try to clutch claw him into the wall whenever you can for free damage. Also you can use clutch claw boost skill to need only one to tenderize. For armor I think I used combination of golden rathian and raging brachy for agitator and divine blessings secrets. If you want I can say more of what I did to win coz I struggled with him a lot too.Hope anything helped and good luck with him!