1st picture: If that's how you start the fight then you are in trouble. The enemy usually takes 2 minutes to group up before attacking, hence the "waves", and as I said, a wall of army ants kill everything. You stay too close to home, which means when your vanguard get destroyed, you can't regroup or retreat, the scientist will be the one to kill you. Start on the right of the tube, when you feel like overwhelmed, regroup to the left. It requires some timing to make the army ants cooldown before fighting them again.
2nd picture: You can see the end of the wave there, the new red dots are respawn. Because you don't kill enough ants to force the AI to retreat and regroup, their respawn will keep coming straight to you, not forming wave. With the way ants move in this game, the suicide squad can make them fight in a thinner line, you can overswarm them that way.
Rapidfire wood ant and stunt leacutter are only good in their niche: killing fast targets like spiders and stunt lock Uber creatures. But using the strategy above is still useful. You need more leafcutter though.