IIRC, the +1 crit range bonus from the pre-U19 Kensei Weapon Mastery III was applied after Improved Crit, so it wasn't doubled by the feat. [See old threat range page for confirmation.] That changed with U19; and it was always unclear if that was a bug or WAI. It appears Turbine has decided to nerf competence bonuses to crit range, among other things. Which might not have been so bad, had they done that right after U19 came out and before people got used to the stacking; but they've added a lot of crit range bonuses since then...