The problem is this:
The Power Strike effect doesn't last long enough to do either of the things it was meant to, which are
A.) Increasing the damage of the next strike, obviously
and
B.) To open up a Special Attack from certain weapontypes that have that opportunity
In the current patch, and likely those before, the Power Strike effect lasts a fraction of a second, and almost never, if not never, is long enough to even affect the one strike it appears for. As it stands now, combos with no effect and combos ending with Power Strike are no different from each other.
Furthermore, weapon types which allow a Special Attack upon receiving Power Strike are given a brief flash of the visual indicator that a special attack is ready before it disappears. Such brief time is not nearly enough time for any of the attack animations of weapons I've used.
Therefore, TLDR; whatever,
Power Strike does not last long enough for any of its effects to be utilized, this needs to be fixed.