I'm just lacking Mars for a perfect Fire Team so I'll go for her
About you Slashleyboy, I would pick Cthulhu hands down, you can even run Cass as your main Soul if you want, trust me I have both Cthulhu and Nike Unleashed and the squid girl gives way better utility than Nike, she just has a Heal, and we both have Ryu-Oh so she's outperformed on her debuff, plus Double Black Propaganda + C Frame(? You'll reach the cap for Defense with Belphegor in your team, you don't even need Sniper Shot, it's an obvious pick for me if I were you.