I'm not you Ally, so cannot speak of your Helper in particular, but let me clarify one point xD

The Power you see when choosing an Helper is a lot lower than the effective Power of the Squad; from what i understood (mostly readin' around the forum, tbh) Affection bonus is not counted in Helper Squad power (they still get the Affection + to stats, but it doesn't show you the bonus). Equipment, as you said, doesn't add to Power to begin with.
That said.. Yeah, 30k is low. It's probably a real 40-45k at most (likely less, though).

Anyway, the way you're doing it is usually how it is suggested to do, and i guess that's what most people do (and should do); so, yes, it's actually very helpful to your friends. Exceptions might exist, though; for instance, say, having a weaker Toad Lily in your Helper can be more helpful in a lot of maps (yes, 12-5, i'm thinking of you) than having an higher-power Knight in her place, even if the overall Power ends up lower. This depends on the girls you have, though. Also, barring the current event, it's nice to have 500+ Speed Helpers, imo.

As a final note, since I'm an odd one, i don't use a separate Set for most missions, but simply stick to Set 1 with full-power Squad 1. Gotta love the raw firepower.