Well, I just had to use "do not advance to next step for x seconds" option in my spam keymap. I use 0.4 to 0.5 seconds, which takes the worst off buffering while allowing mashing my button at my customary speed . I think with 0.7 to .8 there is no noticeable buffering at all, but that'll reduce dps for classes with fast cast time and reuse, like rogues.