Its funny that I made a longer comment in detail about my thoughts about this fight in depth, but some how its gone so I'll try again
Fatalis seems to be the penultimate culmination of IB mechanics, for better or worse. Very aggressive (which isnt bad in of itself), low cool downs, high damage, so frame trap city basically. His moveset is made to punish people who try and run away and drink pots, so the typical IB experience. "Just dont get hit noob durr hurr"
Tenderizing the chest is mandatory for almost every weapon, so no wonder they added the shaver jewel, cause otherwise you wont be able to inflict any real damage even with an alatreon weapon. Why does CC exist again? You dont even tenderize the head for dmg, you can either do it to ungimp WE since the hitzone on it goes up by 1, or try to land your strongest attacks regardless.
Because of how his attacks are structured and the damage they do, you have to play defensively or just get oneshotted. Against a 30 min timer. "Just bait bait out cone breaths noob" Oh so the rajang strat? gonna play a turn based rpg instead of dark souls, at least the latter doesn't have a tight timer
oh also you have to get at least one partbreak before phase 3 or every fire attack will one shot you, even with the fire proof mantle. And he also has a nova for some reason to break up the flow of battle to look at him. So he is a dps check, just with some extra steps
Could be better. Could be worse