Forgot to ask, but did you ever do a "kickstart" roll for both your accounts? It's pretty much you using the first 5 free SCs (after saving Aigis) on a premium summon and hope you get a platinum or black unit. The reason for this is because these units can help carry your team further in the story missions. Some are even OP'ed to the point where they could bring you near the end of the story missions. Some guides, like the one I linked below, say that only platinum and black units are helpful in powerlevelling your other units, but I disagree to that. Sure some golds are pretty niche, but a good gold unit would be Bernice. If you lurk around the other threads, nearly everyone will recommend you use Bernice over Leeanne simply because she is the improved version of Leeanne. And what happens if you pull a silver? The guide says to reroll, meaning to make another account and bet your luck on that one. I, for one, don't recommend doing this numerous time since it's a hassle (trust me, I did this myself, so I know how painful it is to play 3 missions over and over again just to get a good unit).
Of course, I don't recommend you doing this now as you seem to be handling yourself quite well with your current units.
You can refer to VP's free player guide for more info: https://iceinhell.wordpress.com/2015...a-free-player/