Did the event twice and this is what I experienced.
1st time: Flamethrower equipped, followed the zerg and spammed 1 + AoE loot. As did everyone else. We rescued 475 citizens by the end and I had 149 bags.
2nd time: Ran a more serious build and with a small group of friends, saved 70 citizens . And we were able to save 700 citizens total. However, I only received 45 alliance bags.
I believe I contributed more in a small group saving people and fighting away from the zerg. But the rewards were no where nearly as worth it and it seems like most people will just sit with the zerg, because its easy beyond belief and you get so many bags. I’m kind of disappointed with how the entirety of the event works