I did pretty well with
3 x Delta + Ion cannons
in casual games.
I mainly use the Ion Cannons against stressed targets - and of course to get behind targets.
So if the furball starts and there are stress tokens all over from k-turns or other sources,
Those Defenders can be so mean and deathly.
Just don't fly them like you would fly Interceptors. Fly them like you would fly Tie Bombers and all is good.