If you notice the Executor doesn't take up population in space battles, i don't even rely on the fighters the Executor spits out, just bring 5-10 Tartan Patrol Cruisers and they will wipe out all the bombers that come close to it, just set them up around the Executor. Not to mention you will still have population left over for an Interdictor Cruiser or two to throw off any proton torpedoes that get through. That way bombers or capital ships both get wasted.
The A-Wing that crashed into the Executor's main bridge was not the sole reason it died... It wasn't even supposed to do that, the pilot just lost control. At that point the rest of the fleet had already taken out it's shields, so everntually the rest of the ship would have gone down as well, with or without shot down A-wings flying at Piett.
http://thrawn.gamesmod.net Thrawn's Revenge, an Empire at War mod leader
Yes, technically the A-wing crashing into the Executor's bridge wouldn't have been fatal, except by doing so they lost control of the ship and before engineers were able to regain control of it, the Executor plunged into the Death Star due to its gravity pull. But as for the Rebel fleet eventually destroying the Executor in a slugfest, I doubt it. The Executor was damaged, but far from anywhere being near destroyed from laser fire.