I heard PD increases accuracy. If this is true, does wpf only affect speed now?
Really? I don't think so. Having a PD higher than required by the bow helps you to HOLD your aim longer (i.e. the reticule stays at the smallest size a bit longer). But it does not improve accuracy in any noticable way. Its main point is POWER, it gives more damage (recently I had a generation with 11PD, was shit slow, and could not hit much in a distance, but armored guys went down with 1-3 Sharp Bodkins at medium range...
Accuracy (or whatever that guesswork is supposed to be... ) comes from WPF.
And from my experiments so far I would guess that you need MORE WPF for higher PD to achieve the same accuracy. (Another factor for accuracy is the bow - look at the accuracy number, the closer to 100 it gets, the better - heirlooming helps)
The build I mentioned above was fairly accurate with around 100 WPF at PD 7/8, but could not hit distant targets with around 120 WPF at PD10/11
I have not yet tried the extreme PD12-14 builds, I like to put some points into powerstrike, for some surprise melee kills, they are not used to be one-hit-killed with a claymore by an archer... ;-) (well, usually they one-hit me first, just to frickn slow, lol)