Vengeance Fury sounds great. I was just going to suggest it. Always good to have something the character can use to survive when the key to all his nifty abilities up and dies.

I was also going to suggest adding to the DC's to understand the Combat Cant. Since the the longer two partners travel together the more difficult it should get to crack their code. As it is, the difficulty tops out at 20. They may not be gaining any new levels in the class, but the levels and depths of their relationship with each other will certainly continue to gain in complexity. Maybe a +1 or 2 for each language that the partners have in common? Or would that overcomplicate things?