The Sniper class consists of archers from the Sharpshooter class who specialise more in physical damage. Snipers are heavy damage dealers in the game, which is why having a sniper in your party would serve as an advantage in terms of damage.
In PvP mode, snipers are well-known by their heavy damage-dealing skills. For example, if one gets caught in a Charged Shot EX, the player will have one whole chunk of his / her HP taken away due to the high damage. It is wise to maintain distance between snipers during PvP.