Good post but i don't agree with some of those characters you said wernt steeped to far into the darkside to get the effects. Especially Maul who is probably the darkest out of any of them other than palpatine. And as far as Bane he was just butt *** ugly to begin with, But still besides the ugliness he was born with he didn't gain any from the darkside just got the yellow eyes.
While I concede that Bane wasn't the best looking guy before the corruption hit him, he was affected with it. It manifested in a twitch in his hand that showed a future degeneration had he not been killed. It wasn't just his yellow eyes, that twitch/throbbing was the beginning of his corruption. Even Zannah began to have it.
As for Maul, no, he wasn't deeply steeped into the Dark Side to gain the effects of the corruption. Maul was a force of pure hatred and anger, he was nothing but a brute, an animal. Even Dooku says this. He was not a user of great Force techniques like lightning, he was a duelist, a fighter, a warrior. Arguably, so was Bane, but the difference between them was that Bane actually steeped himself into not just the phyiscal aspects of the Dark Side, but also the Force side.