Fatty has the best scaling potential of any land t4, it is almost always good to make another one and put it into your push. The air argument is kinda inconsequential to me because all t4 die to air brutally. I’ve seen chickens die to jesters in like 1 minute.
Is fatty more vulnerable to air? Yeah. But it also has no real mobile land counter. The only thing that activates my almonds with regards to fatty is that t2 arty and tml basically never miss because the shield is fat and parashield hardly serves a purpose with fatty having its own bubble due to overspill. If it got any buff I’d just make the shield a personal one instead, adjusting the mass or hp is crazy to me.
Also if you need survivability for your fatties that late in the game, then make shield boys.
I’d also say the biggest problem for fatties is, funny enough, novax.