I have had characters with 120% chameleon spotted by forest creatures from a surprising long way away. Chameleon can be pumped up to 200% using a combination of enchantments, spells, and potions.
My point is, 100% chameleon is still a little iffy which may add some challenge to the game. I have seen people claim that it ruined the game for them using chameleon.
Sarrah only used it to teach rude townspeople a lesson. She would hit them in the hip pocket with a flare spell from under her cloaking and laugh as they ran around like their pants were on fire.
That's not possible unless some mod is doing it. 100% Chameleon makes you completely undetectable to everything in the game. That's the entire purpose of the effect; it decreases your detection and at 100% you are undetectable. If you were detected, either you did not have 100% as you thought you did (which happens) or a mod is causing it somehow.
Also, anything beyond 100% is wasted and is not calculated anywhere for anything in the game.
Really, even Invisibility is enough. I have stood in a group of 3-4 enemies with Invisibilty as part of my spell chain and drained or blasted the life out of everything (Spider Daedra, Dremora, etc in Oblvion gates... loads of fun).