I kind of disagree on Overpower, although it's better on 1H than used to be thought. I've recently done numerous detailed calculations with it taking into account more things than previously discussed, but I'm saving most of that discussion (and others) for another day.
I think Overpower is a bit better with non-Imperil rapier, and worse with Imperil or shortsword styles, because along with better chances to do damage and build overcharge, it also grants a better chance to inflict Penetrated Armor. In this case I had Overpower similar to Fatality.
Swift Strike is also not to be overlooked. From the beginning in multiple posts
years ago I postulated that Swift Strike grants approximately the equivalent of half the Overpower as a side effect of being able to hit stunned enemies more often. Since then I have reconsidered that as it could be less or no difference if it's not worth it to take the time to intelligently target stunned enemies.
However this past year we learned that Haste negates some of its loss with 1H by in part improving the effect of Overwhelming Strikes, the primary result which is having its +15% damage active more often, but also granting approximately +50% counter-parry. Scaled down to Swift Strike that would be +2% counter-parry, or half of Overpower (this could in turn be diluted along with Swift Strike itself by a factor of 2 or 4 if you have high burden and/or stack with Haste).
IW and Grindfest should not favor Overpower any more as parry comes mainly from difficulty setting (player level and monster PL also matters slightly, if either are too low my elemental spreadsheet found that parry on clumsy species can drop below 19%). It should still be the same 19% ~ 27% (chaosed). IW and Grindfest may have Swift Strike as the surprise champion though, I hope to have more data on this soon.