Wessel V1
Emperor
I think combat odds could better be presented by a chance of survival. This also leaves room for siege units to get a proper xp mechanism. However, winning the combat should always be prefered to just surviving, so I'd give one bonus experience point for winning in stead of survival. Exploits like 99.9% + <0.1% battles resulting in 2 xp should be fixed on beforehand (maybe only give the extra xp in battles where the chance of retreat is above a certain value?), but the system as a whole seems less exploitable.