I think every recommended meta build is 4 piece fatty now with the exception of elemental LBG (just because it's elemental cap is so fucking low it needs Safi), but the build you can make with Taroth Support is so fucking good I don't even bother with the Ala gun anymore. LBG is also the only weapon where the fatty version sucks, but Taroth Support is still so fucking good it doesn't matter
Bow and DB lose a little bit of damage going full fat, but the amount of utility and comfort you gain more then makes up for it.
I still think the Fatalis fight is obscenely overtuned, but won't lie that being able to absolutely steam roll the entire rest of the game is quite fun.