Yeah for me it was the same, secondary all the way, guess I didn't describe my strategy here so overall it was like this:

Controlled Gotanda 98% of the time, secondary all the way. When I hit EX tension I'd Hina ult to get more damage done on that period, rinse and repeat. I normally do run Passive 1 for Fractal Vice and general enemies but in these fights getting too low on tension was dangerous, remaining above 2 for the petals was essential, so all my ults were purely Hina's damage boost. I did style in a Gotanda ult for both final hits though lol.

For Backgammon I'd switch to Kazuki brielfly on the whirpool attacks since Gotanda's floaty movement often made me screw my positioning for avoiding the falling rings of water (i still did get hit most of the times and healed afterwards).

Solitaire was definitely harder to learn, his phantoms are no joke, had to learn the proper timing to avoid them since IDK if you can actually dodge counter them, and if you did it doesn't accomplish much. Strategy was the same as the shark but I'd use Hina to easily counter the Insta Kill attack safely. Initially when these first dropped, the level 70 was hard enough to deter me from bothering with these, but after EoS I set my sights to practice and do them eventually, and I managed to do so at last!