Support - Incendiary Airburst Launcher - Only direct impacts count

Im trying to work the logic out, support is supposed to stay behind and suppress enemies then run round and revive all, but the gadget has to be used within 25 metres or its pointless, so we have to get inside the engagement range to hit something, I wont lie, Im not very good at the game, I normally die after hitting them, and I dont feel like im "supporting" the team while doing this assignment.