If medical assistance is not given to the soldier, they will eventually die. Incapacitated soldiers will eventually come back to your platoon. The key is that the soldier along with his skills will come back to the platoon. Snipers are the platoons best shot. They have the highest chance to hit with their weapon.
Engineers are unique in that they can set explosive demo charges.
They are the only soldiers that can set these types of charges. The way the game determines who will be the medic and who will be the snipers are as follows. The 2 soldiers with the lowest marksmanship skill are assigned to be medics. The 2 soldiers with the highest marksmanship skill are assigned to be snipers. Some weapons in the game work better when several soldiers work as a team.