-10 seems excessive. Maybe -5 would be more reasonable? If I need to take most of the free time given patching up rep, then it would be like babysitting the colony, and that is no fun. Instead of being at the colony, I need to go where I already went and hunt pirates and pathers, and I do that enough already protecting my colony from them. It is not much different than being dog of the state just to be friendly. If it gets too bothersome, I will let rep tank, eat the accessibility penalty, and be hostile with them. Then, after I bore of them, sat bomb (or disrupt spaceport of) all the core worlds and win the game.
As for pirate raids, they can be too effective. In my second game, Asharu decivilized because I did nothing (because my colonies were far in the fringe and I wanted to explore), and pirates raided it into the ground (-9 stability total). It would be nice if I can resurrect it with a colony of my own or whatever, but Hegemony would sat bomb it away (unless I wipe Jangala and Barad off the map too).