I haven't played the game nearly enough to know whether Bushido is truly an imbalanced ability right now, but I do strongly suspect that it is. Since I love putting the cart before the horse, I've already started thinking up solutions to the problem that I'm not sure exists yet. Here I present them for your perusal.
Seppuku: If a unit with Bushido takes more damage in a melee battle than it deals, it will commit ritual suicide at a LEVEL * 5% chance.
Ronin: If a unit with Bushido takes more damage in a melee battle than it deals, you will lose control of it and it will wander the country-side picking fights with enemy units for 30 turns LEVEL * 5% of the time.
So, do you like the cut of my jib? The latter suggestion was actually someone else's from reddit.com/r/civ.
Seppuku: If a unit with Bushido takes more damage in a melee battle than it deals, it will commit ritual suicide at a LEVEL * 5% chance.
Ronin: If a unit with Bushido takes more damage in a melee battle than it deals, you will lose control of it and it will wander the country-side picking fights with enemy units for 30 turns LEVEL * 5% of the time.
So, do you like the cut of my jib? The latter suggestion was actually someone else's from reddit.com/r/civ.