If we assume the Horror at Dive Rock and her offspring from Solsthiem are related to Trolls, then some of their kin are able to use strong Chameleon spells (which may or may not be genetic) and fight using the severed limbs of slain enemies, using them as crude tools.
It's possible they're of an average ape level intelligence, but not sapient.
I dont know about that... Brijj Tole troll might not be such an anomaly. As for the argument that he was visionary because he was charging for septims--- I could dispute that as well. Gold is pretty shiny afterall. Having lots of shiny things could make him seem sixy in troll society, if such a thing exists. (which I think there are enough subtle hints to suggest such-- but something akin to cave-man like society.)
More telling, is the fact that Brijj Tole troll has grasped the abstract notion of written language. Humans didnt use written languages for THOUSANDS of years. While apparent that he did not CREATE the language, the fact that he can employ one (however poorly) suggests that not only that trolls have limited sapience, but that they are also capable of being educated.
Capable of being "Reformed" is a whole other ball of wax though.