If youre going Warbow stick with the build you just stated.
I'm currently
Strenth=18
Agility=21
IronFlesh=4
Atheltics=6
PowerDraw=6
Weapon Master=7
What it really comes down to is what you want to do and what youre capable of doing.
I feel I can aim really well and so 163 WPF with a Warbow at level 30 is sufficient enough for me to still dominate and land arrows on target. If this isn't you then I suggest a lower level bow which shoots faster and may have better accuracy.
For me I personally enjoy being able to bring down any target, from lightly armored to your heavy armored knights. You just can't do that as easily spamming a Khergit or Strong bow. Where I do have trouble however, is fighting against other archers as a large majority now use Strong or Khergit bows which spam arrows fairly fast, faster than the warbow. I found though if you know how to strafe around you can overcome this and use superior aiming and damage to beat out other archers with faster bows.
So in the end like I stated it comes down to what you want to do, I would recommend you just go Power Draw 6 regardless of what bow you use and test out both the War Bow and Strong Bow as I feel these are the only two bows worth using at this point in time since the patch. Also don't make a set decision until the upper 20's as to which you find most viable. Infact I wouldn't decide on either bow until level 30. From then on you will be able to figure out which bow you would like to use permantly. With your bow selected you can then alter your original build to better fit your playstyle. I hope this at least helps a little bit.