Obviously as the numbers dwindle, it will be obvious and the larger zerg will just run you over with no threshold line. If they don't see a sea of red, they won't hesitate.
All you need is good heals and pulls. Even with zerg vs zerg there's that threshold line in the middle only few will cross, fearing they will not get valor if they are the first to die. So most try to stay ranged until one zerg is obviously overtaking the other.
If you kids would quit being scared of small group pvp, maybe more republic would come to ilum. Or you can re-roll on my server where when the republic make a group half the size of the imperials they wipe them.