What's the point in getting +10% glancing blow damage if I can get 5% doublestrike using a 2H?
My point is, Perfect TWF gives you 5% stacking Doublestrike on your main hand, I really want to believe devs tried to make it work only with one handed weapons. In the other hand Perfect THF gives you an AWESOME 10% GB damage (and 10% chance on triggering effects, I know) */sarcasm*
10% gb damage is good ok, but it's nothing compared to 5% doublestrike, or to the ability of bypassing some damage reduction. Not everyone takes THF feat line, maybe a fighter or a pure barbarian, so, what if I choose to roll a Quarterstaff monk or Greataxe Paladin? That means I won't have THF feats, at least not all of them, and that makes Perfect THF a ****.
I believe all experienced players will choose perfect twf over perfect thf (because it works with two handed). I'm not asking to change PTWF but to take a lovely look at PTHF. That's MY opinion.