Is it useful to raise Mind Magic with sced armor on my body sorc in order to get less resists on my blue spec ae mezz level 24?
I tried to ask in game, some said yes, some said no.

It is known that for baseline spells that +skills is useful (eg. DD spells do more damage, charms get less resisted), so i made some test with the Spec Body DD on the level 50 doll to see what would have changed. Basically with +7 body, instead of +2 (same int) the damage was slightly higher.

So now I am wondering: since that +body DOES affect the damage of a spec spell, shouldn't it also affect the resist rate of it, even if it is spec line?

can anybody help?

As far I know the only difference you can get raising the composite spec on mind is all about the focus and the waste of mana. You won´t get it full 50 focus 'till you get high RR. Talking about miss rates I never noticed any improvement from having or not the bonus really.

Another thing is the pet charm, where you can really notice it. Anyway if you are 45 body or 39body it will be the same crap a little improved with the composite spec.

PS: Getting MoF also helps.

Resist rate depends on the spell level (and target level, and mof) not on the spec level.
So no, +mind wont affect your mezz resists. It wont affect the mezz duration either. The only thing that gets affected with +mind is charming. But you can make some additional items, you put on for charming to save the slots in sc.
Mythic even removed the pac gems of the healer, for that reason. +pac wont do any good at all as there are no spells in that line, that would profit of +skill.