Surviving VS. MedusaTIPS
I was having trouble surviving at first and thought I'd share my solutions. Maybe they'll help someone else.
From what I can tell, back row only gets petrified by Medusa's counter attack. So units that don't attack (like Maat set to slide) should never get petrified in back row. And Mars and Dana will be petrified less often. Putting Maat and Leda in back row led to some stellar regen! 😲 Setting drive to Luna only can help. Also, setting Luna to Slide - Tap - Tap seems to help, because her slide ATK increase lasts two turns and healing petrify with tap may be more valuable than random skill gauge increase (?). Hope this helps somebody, good luck! Edit: Also, Sytry has a tap that will remove ATK buff stacks which can make a huge difference if you set her to Slide - Tap P. S. The black spot in my character lineup is Thisbe. For some reason her icons stopped displaying 😕 Something to do with uncensored patch I think.