Hehehe, depends. At the beginning, you are ok with one. Then what I usually do is that I give my Heavy second class “Sniper” and I make him carry Canon and S.Rifle at the same time. I use this to get me Anu aircraft ASAP, then I get second Sniper and I give Heavy 4 grenades and Boom Blast instead of the Sniper Rifle. Then it escalates kinda quickly to the time where you acquire NJ Sniper Rifle which has piercing damage. Also IF you have Chitin Armor+Living Weapons DLC, you get Acid AR basically on third game mission and that can help you too 
and that’s the problem. I got two sirens and additional company (2 crab+triton if I am correct) on the living weapon mission (which is CQB). thats why I hate them. so I am waiting for AP from NJ, which I got right now.
The second mission is a lair. You can basically wait them out on overwatch till they come to you/snipe them across the map.