Thank you for the report!
Are you sure the FPS remains bad when no fighters are on-screen? They'd have to be a little ways offscreen to not render at all, btw - not by a lot. For the sake of testing, though, having the screen be say a half-screen away from the nearest fighter would ensure they're not rendered. It's just odd for the "jitter" calls to be affecting performance when the fighters are offscreen since they'd generally not be rendered then.
It's also strange that there'd be a difference between the Broadsword and the Lux - unless the Lux have their shields up, I don't think there'd be any meaningful difference. Hmm.
Regardless, though, unfortunately this looks like a driver performance issue. It's just not doing *that* much more work for the jitter effect, so I suspect it has something to do with how the card is handling transparency/blending or some such. My apologies - I don't think there's much I can really do about this on my end.