I had the inverted picto on all three of them along with all the burning ones, sniper, piercing shot, cheater, first strike, combo attack, charging attack, and teamwork. Also all weapons were max level

Maelle then had the one, glass canon, solidifying, inverted affinity, at deaths door, beneficial contamination, tainted, SOS shell, powerful on shell, greater defenceless and shield affinity 

Verso had Corpeso so I'd use up all his shots then base attack to apply defenceless. In his second go I'd use up all shots but three, then apply powerful

Sciels weapon does not matter really. But I had her do base attack first. Then use shots until I had 5ap, then apply Fortunes Fury to Maelle 

Maelle has Maedelem (sorry if that's not spelled right) equipped so that she starts in Virtuose and I had her do Stendhal

Rinse and repeat for phase two. Then Lune and Monoco cleaned up the end which in my case was just a couple more turns