I think the trick to using Satori is pairing her with people where she can abuse and make the most of multiple things
Unfortunately most of those pairings don't work that well. Double Charge is 66% hp damage to the row (VERY not good), Galaxy Stop will still eat the front line's ATB (it's formula pierces some mnd but really isn't special, and she'd have lv0 status infliction rates), and sadly, without possessing any damage boosters (apart from weakness boost to let her hit "normal" damage instead of lv0 damage... if she can hit weakness), her bad level rate, and her only moderately good offense stats, 300% attack formulas really will only do about as much (or more likely, less) than what any good attacker can do. The 400% attacks, Judgment/Giga Flare, and 3D Super Scope/Master Spark are the only truly -useful- copy attacks, and two of those are only special against the really tanky bosses. Even Mountain Breaker just manages keeps up with what other characters can pull off- which is not good considering Satori can't take a hit where most characters can, unlike LoT1.
...speaking of that, oh, huh, using her with Yukari's Spiriting Away is actually nice. I suppose in very specific parties (Yukari+Nitori+Marisa+Eiki and/or Utsuho) you might collect enough useful blue mage moves to justify a party slot. With the right equips her HP can be enough to keep her out in the front safely for a short while, so if the value of piercing defense is enough, or if you need a second Spark... (Or you're being silly and Spiriting Away a bunch, which sounds potentially neat) ...but there's still the issue that she's only a little better than a glass cannon, and the actual glass cannons generally do better and are hard enough to use as it is until you get awakened Keine. Spiriting Away is what manages to tip the scales a little.
Ran's composite spell actually won't do much since experience has told me that splitting resources between ATK and MAG isn't viable. Even if you went pure ATK / MAG and used a composite spell, after seeing how underwhelming pure MAG Galaxy Stop is, there's almost no way Ran's composite spell will fair much better on Satori.
You always go all in on the higher offense stat for composities, and then use equipment that boosts both when you can. That being said, the move isn't half bad (A decent rule of thumb for composites with roughly equal base offense stats is, cut the influence of the lower offense stat in HALF, and add it to the other, so it's roughly 265%, which is... not bad, but not special. Sorc can make it good with +30%, but since it's on Satori, it's not like she can use the low delay much.) It's great on Ran but stay-out attacks don't really work for Satori who must get in and back out or just die.
and yeah, boosting the front row's weakness hitting is nice, but with her durability it only works in HP Wall Form. If she had some more tanking ability it could be pretty nice. As it is, it's -possible- you might get decent damage out of running her as a wall when you combine Awakening HP Damage, boosting weakness hits on the party, AND doing some form of support herself (herbs of awakening?). She ignores all the self-buffing bosses in postgame, but she has no damage reduction or regen to synergize with her HP... :T Even as a "tank", she looks to capitalize on weakness boost and HP damage to, in actuality, be an extremely unorthodox attacker herself.