If it takes a decent number hits with 5-6PS, but it's not going to take many less with 8.
True dat. For instance, let's look at a target with 60 armor and 75 hit points (typical crutch stats), un-held torso strikes with no speed bonus, 110 effective wpf:
With 6 Power Strike:Takes 12 swings to kill with a 33c weapon
Takes 6 swings to kill with a 34b weapon
With 8 Power Strike:Takes 10 swings to kill with a 33c weapon
Takes 5 swings to kill with a 34b weapon
...not a big difference. The higher athletics/wpf allowed by the 6 PS build probably made it easier to land those 1-2 extra hits anyway.
Meanwhile, same calcs but this time assuming held strikes to the head with +20% speed bonus:
With 6 Power Strike:Takes 5 swings to kill with a 33c weapon
Takes 3 swings to kill with a 34b weapon
With 8 Power Strike:Takes 4 swings to kill with a 33c weapon
Takes 3 swings to kill with a 34b weapon
You can see that achieving held strikes/headshots/speed bonus is far more important than power strike! And it's athletics and wpf that enables these held head strikes with speed bonus. Also that low cut damage swords are pretty damn good if you can deliver held strikes to the head (watch San and Rusty play; they may use fairly weak swords, but every strike is a hold to the head).