Does it need lvl 15 for max ias on thrower barb and bowa?

14 is same EIAS as 15
The difference is only a minor extra ed/ar%

Here, use my calc for doublethrow:
https://sins-of-the-sun.github.io/double-throw-ias-calc/?mhWSM=-20&ohWSM=-10&mhIAS=30&ohIAS=30&offWeaponIAS=70&fanaticism=33&frenzy=0&markOfTheBear=0&burstOfSpeed=0&holyFreeze=0&decrepify=0&chilled=0&slowPercent=0