Like Big Pistons, I don't think all partial failure should be handled the same as a complete failure. I think partial failures have two divisions: CAN maintain altitude, and CAN'T maintain altitude.
In the CAN'T case then it's like a total failure (but with better glide performancen, and an extra option to adjust vertical navigation)
In the CAN case then an immediate landing is not necessarily the best course of action. There is an option to continue flight, albeit with a considered possibility of it becoming a forced landing anyway. I've had a partial failure in an A36. Even though the engine had a whole cylinder separate, the aircraft was still flyable. Over rough terrain at night - as I was - I'm certain that choosing an immediate forced landing was, and still is, the worst option. Instead I was able to make it to an airfield. But the whole way I was prepared for it to become a forced landing, and tracked as best I could via open areas.