In Korraks, if both teams just zerg with 0 defense, alliance will win. There is just less PvE stuff for them that eats so much time. However, defense does work, especially in towers. While leveling my druid as guardian, i could single handedly hold IBT against multiple people until the rest of my team was already pushing into DB.
Alliance likes to just kite the commanders in the towers without taking the time to kill them as a group so any tower defense just needs to hold long enough for the commander to leash back and 2 shot everyone.