2 Scouts = 1 Tac dps
1 Scout with Shotgun = 1 Tac dps
1 Scout with Shotgun+Sarge = T2 Tac dps
2 Scouts with Shotguns = 2 Tac dps
Not that Tac dps is anything special

Vanilla: Good sight and speed. Low dps in ranged and melee. Use for capping and occasionally adding tiny amounts of dps to a fight.
Shotguns: Good against melee due to blast and is also good against generators due to the dps increase. Upgrading two at once can lead to a timing push by itself.
Sarge: Detection and a grenade that's useful against buildings and as a melee deterrent. Useful with Shotguns as the Sarge will also equip one. Adds some survivability as well, but not really a reason to get it for that alone considering the price.
Infiltration: Good for Scouting and stealth capping. Increases health regen to the point where you can keep them on the field forever unless forced off.
Snipers: Good for long range burst damage but not high dps. Setup time makes them vulnerable to being targeted so have to keep them back.
By the way, what commander were you playing? Makes a HUGE difference in how you use your army.
With FC you want to have him spearhead your army and then move up your Scouts behind him so enemy units automatically target the tank rather than the squishy Scouts.
With TM or Apo you would use them much less aggressively and would either keep them back as vanilla or get snipers. Shotguns if you know a melee unit will be coming to you.