I think this Master fight is quite underwhelming and I have an alternate suggestion for the team that could be used:
Unicorn Vivifier [Rez allies and Damage dealer]
Unicorn Holycaster [Healer]
Emerald Paragon [to increase damage dealt, favors this team with the mastery trait]
Mite Gravedigger [extra rezzing chances]
Unicorns should be hard to kill, but right now, just take out the one vivifier that’s on the current team, and keep it dead if another uses a rez spell and it’s too easy.