as for the outnumbered/gunned rebels:
maybe mor action from the cannons/batteries would improve the impression, that they not just throw rocks at mountains ... ?
http://starwars.wikia.com/wiki/DF.9_anti-infantry_battery
http://starwars.wikia.com/wiki/1.4_FD_P-Tower_laser_cannon
setting up the "defense-tench":
http://img2.wikia.nocookie.net/__cb20131006055952/starwars/images/7/7e/EchoBase-TCGtSfS.png
even this picture gives a different situation, or not ?
http://img1.wikia.nocookie.net/__cb20070612034839/starwars/images/e/ee/Battlefront_promoart.jpg