They need to 2-tap and use special ammo (4 rounds in PvP to start). Likewise, in PvE, they should hit like a truck. The only weapon type with a longer range with a similar role is the sniper rifle. Scouts should be near-peer with snipers and then people will start using them. All those weapons that Bungie included in the quest step with scouts are like a self admission from Bungie that they made them the shittiest weapons in the game. Every one of them needs a buff - not necessarily a damage buff mind you.