Is "stunt dice" unworkable? Nice terse ring to it.
Don't really have an opinion on 'Combat Superiority'... but I will say I'm not a fan of the term 'Deadly Strike'. Especially when it sits next to 'Parry'. Take off the deadly part, and just make the two uses of expertise dice 'Strike' and 'Parry'.
That is my naming convention whine of the day.