Mk:3s are easy, even before the hammer update. They absolutely suck with the sword. You run up beside them and do a side swipe while turning towards them.
Steps:
1: Run towards the side of the Archer
2: Perform side swipe.
3: Look the opposite direction of the side you ran up to (If you flanked right, turn left and vice versa) while performing swipe (this makes the swipe longer).
4: Mutilate body