I consider possibility, that TB can involve offensive (active) and defensive (passive) missions.
Offensive ones are where you need to advance and use your best teams, so, of course, G8 NS squad can do 1/100 of dmg comparatively to G11 Rebel/Clones/Jedi/etc. zeta squad. For this kind of missions, it is better to have one meta squad than dozens of undergeared ones.
But defensive ones are smth that doesn't actually require viable toons, but only the amount of total power you can assign to the particular territory in order to protect it. I have this theory, because of the power rework when now every piece of gear, mats or anythings gets some indication in the total amount of power. It can be like following: to advance and conquer the next piece of territory, you first need to hold (protect) the territory you've just obtained. It means that you should assign total of, for instance, 500k power to it: every guild member chooses some toons as defenders of the given territory until there are 500k power total. In this case even lvl 1 1* unlocked characters matter.