Insect Glaive dodge delay

[Thug Killadome]

Was playing IG and though I was thoroughly washed when I failed to i-frame roars even with EW3...but noticed I could make it through with less or even none on HH and LBG. Went into the training room and sure enough, there's a noticeable delay of a few frames after hitting the button before your hunter actually rolls compared to other weapons. The only imaginable reason I can think for this is to create some kinda buffer to make vaulting easier (you can hit the buttons in the opposite order and still get the vault), but considering vaulting already has a modifier button (RT on pad), why would they ever need to include a buffer that just kills your roll?

Wasn't nerfing the moveset and forcing Triple Up bad enough? Does someone on the dev team have a vendetta against IG or something?