Revealing mistake: In the last episode, 'Chosen', Anya beheads two Ubervamps. The second time she swings the sword it very noticably doesn't go anywhere near the Ubervamp's neck, closer to its stomach.
Revealing mistake: Early in the final fight, Vi makes a flying kick to knock an Ubervamp off the cliff. As she lands, she swings back and twists slightly, suspiciously like one would do if suspended on a wire. There is no way she could gain this motion by kicking straight off the vamp as shown. (00:29:00)
Answer: She has superpowers, ergo fast movement. The reason she outruns him so easily in "Touched" is that she stops trying to actually fight him and just dodges instead.
Shay