Mute, the Silent One is an ability power caster who excels and bursting down crippled enemies and disrrupting enemies during teamfights.
Say No More allows Mute to counter-harass the enemy during the earlygame as it can be followed up by a quick Hush or Punishment. The magic damage associated with Say No More is almost a joke. The one second silence has to be capitalized on. Also, I doubt that anyone that's not fed maybe except an assasin or mage, could deal 10% of you health in 1 second.