Though huntress is not bad, but she is completly outclassed by icefang huntress so you would be useing stones to promote a charater that you would want to immidiatly abandon once an icefang event rolls arround. -- and because she used Kings that is not a luxury most people can afford, or well, they wouldn't want to.
The Huntress, i agree, is a useful unit.. I cannot say much about it since, unlike Secret, I do not own one.
Statwise, the Huntress does seem better with higher HP and DEF, however the argument in favor of the Sniper is her range and the 'Warning Shot' passive at champ which gives her 15% more ATK stat. The Huntress's 'Into the Fray' passive at the same rank isn't too helpful in most cases.