If you’re playing with AI, you’ll quite possibly end up doing the most damage. What’s great about playing on your own is that you can swap between characters as and when, so you can lay some traps as Maggie, swap to Assault and deal some damage, swap to medic if the AI isn’t healing well enough etc.
Maggie was a “main” of mine for a while, and if you’re struggling to get to grips with how and when to use the harpoon traps, you might want to try Wasteland Maggie - can only have 1 harpoon in the ground but has a much longer range. Daisy has a flame thrower, the harpoon when attached does damage and I think her weapon might do some DoT (but not very sure on that last point). Her strategy is kind of harpoon, then shoot, then place the next one shortly after the monster breaks it.
With standard Maggie, you don’t ALWAYS need ALL traps out, and there are opportunities to sit back a bit and dish out some damage, but as a general rule you want most of them out. Especially if one of your team mates is taking a beating. What’s hard about planting the 3 traps is trying to make sure they hit the side or back of the monster, and not have multiple hit the same place at the same time, because they’ll get broken super easy. Having 2 hit, 1 on either side is absolutely fine though because it’ll be a pain for the monster to take out!
Gotta love playing all trappers because your job is to make moving miserable for the monster, and that’s just great