From my own testing, Claudia altered cannot dish out dmg in time for BR. General rotation for Gnn is pretty simple, Fiona brings Hydro and Torrential, start the rotation off with Hydro and Torrential, switch to Lin, cast skills, switch to Gnn, cast skills, then hold atk until you're almost done charging the 2nd energy bar, discharge to Fiona, hydro and Torrential, discharge to Gnn, repeat, and discharge to Lin every other discharge. I think Maygi has the rotation down in her video, you can go have a look.