!!!
I use a similar team, actually! It's Nino, Olwen, Olivia, and (currently) Roy.
What are your builds for them? I run Desperation/Fury Nino, and I can't change that. Olivia can Dance like your Ninian. I can try to emulate your Rein build into my Olwen, though. Do you run Death Blow on him? What assists do you run?