Any physical weaponskill can multi-hit with very few exceptions. Weaponskills cap at 8 hits (so asuran fists is 8 hits natively and will not increase in hits). Double attack adds an extra hit, triple attack adds two, quadruple adds three. A one hit weaponskill also gets an extra hit if the person is dual wielding. Say you are dual wielding, use a one hit weaponskill, and get a double attack proc, it will hit 3 times.