He's using the Fencing Mastery "Pierce", to knock Travesty down to 0 Stamina, which significantly slows her attack speed. Pierce damages 30% of the victim's max Stamina over 10 seconds, although it can struggle to lower the Stam of creatures with Paragon level regen. He has a shield equipped, so that when she turns into him, she can't parry for crap (since Travesty has Bushido).
I'm quite curious to see how a Macer and Fencer together would do against Exodus. They'd be X-Healing each other, and keeping Stagger and Pierce on Exodus to destroy his melee damage output.