I’ll be brief with this one.
Summary
The team building AI seems fairly atrocious. The AI will sometimes spam units whose synergy can be nearly impossible to beat, namely Sirens. There are likely a lot of improvements that could be made, but it’s hard to make them without knowing how the system works.
But here is an obvious one that’ll solve the issues:
Synergy Cost
Adding one siren to the team might cost 100 points. Adding two sirens, however, would cost 500 points, because sirens synergize with each other very powerfully. You can do the same for mortar crabs or the like.
This will increase mission variety, as overpowered focus builds will be smaller and rarer.