What about us humans and putting missile turrets under forcefields, especially higher mark ones?
IIRC, our missile turrets decimate AI raid starships too.
In particular, the AI doesn't have any damage reduction from firing out from underneath forcefields. Let me be fair: in my test game, I did encounter systems with this "Venn Diagram" of death from forcefields, missile guard posts, and fortresses, but it didn't bring my game to a screeching halt.
Missile Guard Posts are in a weird position in the triangle, they counter medium (spire), neutron (zenith), polycrystal (heavy bomber), and ultra-light (raids). Normally, countering them with plasma siege starships works just fine even if they're covered by a FF, and various other methods can clear them out if covered by a fortress. But that said, if they get FF and Fort coverage, they get a disproportionately large effect. Remember, AI Forcefields do not cause damage reduction to units firing out from under them. It is still entirely plausible to crack these systems without pulling out your hair, if I force myself to avoid exaggerating the difficulty of these systems. I did however unlock multiple MK3s, so that helped.
Really, I just think that it would be fitting to give low-level Raid Starships a role to fill in the current rock-paper-scissors guard post balance. Necessary? Nope. In other threads, you might even see people talking about buffing Raid Starships in a much more general fashion again. This wouldn't necessarily preclude that, but it would be a role-based buff, rather than a stat-based one.