Because I'm contrary, I thought of this squad:

4x Onyx Squadron Escort - Unguided Rockets - Autoblaster Turret - LWF

Is it garbage? Or worth trying? Mostly just want some opinions before I blow my money on 3 more Aggressors.

It's not worth it. You'd be better off running a regular TIE Swarm, or triple Defenders, or almost anything else.

There's nothing special about these guys, bumping them up to 3 primary that ignores range still means they need to get people in arc, which means they're in the thick of combat, which means they're exploding pretty quickly.

If you're buying four Aggressors, you're really looking at Quad TLTs... And Y-Wings probably do it better.