I for one am glad that Gouki(Akuma) has weak defense, because if he didn't, he would seriously be an extremely strong character. I mean, let's just say for example if he had the defensive and stun bar of someone say Ryu, well...with this simple upgrade alone, it would shoot him up the tiers listing. This would mean that his badmatchup with Makoto, would no longer be such a bad matchup because Gouki's low stamina was the single reason why Makoto can eat him alive.
If your talking about rushdown, Gouki simply has basically the best rushdown game in 3S. He has so many options, that he simply needs this weak defense and short stun bar so he wouldn't be so overly powerful. I would say that if he had the defensive power and stunbar of someone like Ryu, Gouki imo would easily be in the Top 4, either tied with Makoto, or even being better than her, and maybe even on par with Yun, Chunli and Ken.
Gouki is still very strong, I do remember in Japan they ranked Gouki 6th overall, the only characters better than him over there was Yun, Chun, Ken, Makoto, and Yang. I mean, if he was to ever get an upgrade in defensive power and a longer stun bar, then he would need to recieve some other form of a tone down, because with these boost and no tone downs after then, he is easily going to be one of the best characters in the game.
Besides, Gouki had his time, he was easily #2 in 2ndImpact, with only Ibuki being better than him, although those two where easily Top Tier. I mean, I could just imagine if they left Ryu with 2-stocked denjin and if my memory serves me correctly, the denjin bars where shorter than the one in 3S as well...this would've made Ryu a monster in 3S. Ex-options + Denjin, or 2 fully stocked Denjin would pratically mean 1 round guaranteed if the first one landed, but oh well, I don't mind playing Ryu the way he is in 3S, still good.
Renesor I don't understand why you would want to downgrade Gill, because he is the boss of the game and he's supposed to be ridiculously overpowered. Plus he's not tournament legal anyhow, so it doesn't really matter. I mean, he's equivelant to Gouki in SSF2T...well, maybe not as ridiculous but he's up there, I don't mind Gill being powerful, as stated before, he's a non tournament character and he's a boss, he has everyright to be overpowered.
On a note, imo, I believe in the US, we are severely underplaying Yang, imo, he's better than Yun overall...however since Yun has the Genei-Jin super, that makes him #1 however if you where to remove that it would be Yang>Yun, the younger brother has so much potential but he's overshadowed by his Genei-Jin older brother.