During Focus Fire, her moving is stuttering extremely, and even comes to complete halts frequently, especially when having to curve around obstacles.

If you repeatedly change directions while moving, you can already observe a stuttering on her, and sometimes even a short delay before she reacts on the move command. It's much worse when she has something blocking her path so she has to turn or curve around it. This can be anything, units, trees, cliffs and artificial blockers created by spells (e.g. fissure)

In this video, I have made the paths visible, so you can see what's happening. As you can see, upon each attack she launches, the path gets re-calculated. This means when she has to walk around something, she stops several times, heavily slowing her down.

In this second video, you can see that, even without obstacles blocking a direct path, repeated turning causes stutter, too, slowing her down.