Also, I'm not sure how much this applies to helldivers specifically, but from what I've seen, teams didn't really teamwork. Because they didn't have to.

This can be very bad because if it follows these steps:

1. game is easy, no teamwork required, players learn to play the game without teamwork
2. game gets harder, but some people can still manage solo, complain about "newbs" and tell them to "git gud"
3. game gets even harder, now it's impossible to play "quasi solo" but the environment is no longer fit to learn teamwork in the context of this game. "How" to work together effectively.

Then people will complain, justly, that they don't have the tools and methods to beat the challenge. Which is correct. They don't. But you can't just tell people to "go play easy mode and learn the game", when they are "max level" and put 40-100 hours into the game.

Of course the synergy tools still have to exist and I'm not knowledgeable about helldivers whether they do.

There is no good choice to "encourage" teamplay, except via creating "natural" funnels that people will "end up at" "organically", and putting a challenge in front of them that they can only work with teamwork. But that means the challenge has to beat them, until they get it. And that may never happen.

One game I have found exceptional as a case study for what is "overpowered" and what isn't, and why, is magic the gathering. All the "code" is public. The complaints are public. The bans are public, and explained. So if anyone here wants to nerd out about balance and doesn't know mtg yet, there is a rabbit hole for you.