And ampies and affection aren't calculated for helper squads, thats why most of ~70K TP helper squads seem to be twice as powerful as my own 80K TP squads.

Total power is a poor way to rate girls to be honest. It's weighted too much towards high hp girls that may not also have the atk / def to be useful.

I actually find ranking them by ATK high>Low is better but even then certain passives are far stronger than others (like skill activation rate or enemy atk nerfs).

The proper way to determine the value of power should be based on how you weigh each stat, and then also how you weigh the value of the passive and active skills.

I'm too lazy to try to put together a spreadsheet to calculate the "value" of each girl, especially since you'll need a lot of number crunching to determine the value of affection, evolution and fully unlocked skills.