Just get to the second level both the huntress and the tank, get anyone as leader but be sure to have tank and huntress in the team.
This is easier if you have the upgrade to exclude upgrades but anyway it boils down to these main points:
1. Upgrade both the tank and the huntress weapon to complete the first two variants
2. get the rocket launcher for the tank and the explosive arrows for the huntress
3. if you can, stack up fire rate and reload speed via perks or items, even the swat as main can work
4. just play normally, the explosive arrow has a delay before it explodes, eventually the rocket will hit a target that have an arrow into it
You might boost your changes with the land mines and the greneades from the swat, this is however unconfirmed and relies on abilities cooldown.