I find that this composition of ships for the Rebels is death on Space Stations 1-3, maybe 4 as well.
1 Mon Calamari Cruiser
1 Fleet Commander
4 Corellian Gunships
4 Y-Wing Squadrons
4 X-Wing Squadrons
4 A-Wing Squadrons
The Mon Cal should hang back and hammer the station and any ships protecting it from afar. The gunships, with their engines boosted, should run around the enemy ships in a frenzy, shooting down fighters as they spawn. A-Wings will help them in doing this by using their sensor jammers and leading the fighters straight into the gunships' sights, while the X-Wings shoot down any fighters or bombers that spawn from the space station. This give the Y-Wings some room to take down the station's shield generator and hangar, leaving the way open for the Mon Cal to move in and finish off the station and the enemy ships.
Usually the losses for me are:
2 X-wing squadrons
3 A-Wing Squadrons
1 Y-Wing Squadron
1 Corellian Gunship*
*This is only if they have Piett, because he uses his proton beam to destroy the gunship.
I usually build three or four of these fleets, as they are good and softening up systems before your main fleet comes in.