Finding Atalanta is pure RNG. He might find her next Advent, he might find her next year, he might never find her.You do realize that Herc's nuke scales in proportion of your damage, right? So if it's only doing 300k, then it isn't weak - it's probably worth ~2 turns of your damage output. And that's no small thing in GO, since there's often some extremely dangerous enemy that has to die ASAP!
Overall, yes, Andro can help newer players do things they wouldn't be able to do otherwise. But your grammar and reasonings for it are... lacking to put it mildly. Anyway, I still wouldn't recommend Andromeda for newer players - just roll with Cass if you need the healing. Don't get Andromeda until you have the basics down, and Herc's self-buffs are so damn powerful that even without her Relic, she's well worth her place in the "basics" section.
Also, reminder of the The "which Soul should I use?" thread.