I think rasing stability doesn't really do anything to affect the hazard rating which only affects upkeep? Stability only affects ground and fleet effects doesn't it?
It always struck me as odd that you could have a population of billions or tens of billions, yet the colony would still have the decivilised modifier. At that the point the original population would be tiny. If actively resisting they would have been eliminated by ground forces a long time ago. If disruptive, their effect must surely be less than any amount of organised criminals in your world. +25% hazard rating seems completely overblown, on the same level as various hazards like hot that necessitates specialised equipment to perform operations, complicating life support and infrastructure. If it transfered to a stability rating to represent that entrenched population it would make more sense.