Maybe either get rid of the Counter, or make it so it only counters Sword-wielding enemies? ...Though that might seem a little restrictive, actually...
*looks up the skills*
Well, with their skills combined, it'd work more like a Pavis or Aegis skill. Halves damage from Sword, Axes, Lances, and Daggers...
Would this work?
Life-on-the-Line (Sword Mastery didn't make much sense here to me)
When HP is half or less, counters Sword, Axe, Lance, and Dagger damage, as well as any stat reduces done by Daggers.