I'd say Battlemaster expresses the exact same thing Blood & Power suggests. Blood will invoke in most people the idea of fighting or Battle. Power is more likely to suggest something other then fighting, but when you pair it with Blood I'd say its no different from implying that being a Master of Battle gives you Power through Blood.
It also sounds kind flat compared to Battlemaster, but I guess I'm partial to the name already.
I have nothing better to suggest though, so I suppose my opinion on that only goes so far.
Blood has the double signification of blood lines and nobility, and of battle and bloodshed. And power, well, speaks for itself.
