Gau 'sucks' in 1994 when you are 10 years old and doing a blind playthrough of Final Fantasy VI.
But it's 2023, and we have 30 years of experience playing around with Rages; we have YouTube and Giant Bomb and Discord and GameFAQs. We can look into Final Fantasy VI like an extradimensional being and dissect it down to the assembly code. We can use Gau, now. We have the technology.
Gau is good. Gau is great! Gau is OP. Sure, he has 253 rages, but you only need, like, five of them. Gau can cast Meteor, Holy, Shock, Firaga/Blizzaga/Thundaga for free. And if spells are too fancy for you, he can hit like a truck.
Gau cannot fail, Gau can only be failed. All hail Gau.