Sorry I was being pretty vague. I meant why doesn't Burst Fire activate from Ranged powers.
Ranged powers are not classified as ranged attacks, at least not as far as epic talent triggers are concerned. (And there are some very good reasons players should prefer it that way, which I will let you consider for a bit.)
Musketeers are not intended to function exactly the same as Witchdoctors, and vice versa. There are upsides and downsides to every class, talent, and power.