That build looks good to me. 4 Power throw is really nice. Mess around on the damage calculator; 4 PT and loomed Heavy Throwing axes can kill many people with 2-3 axes, whereas 2 PT with franciscas or war darts won't be killing anyone but peasants.
I say if you can't get up to crossbow damage, don't bother with throwing, just grab an xbow. 4 PT is where you start to match crossbow damage, with a higher rate of fire (less ammo and range though).