I would say I struggled in "Deus Ex Machina" and "Heart of the Machine". Playing through on hard is insanely difficult and I lowered to Normal. My tactic ended up having Fixer and Scorch slice Terminals while Sev and I shot the droids. (Ah, I knew saving the Heavy ACP MG repeater would come in handy). As for heart of the machine, when I first got the game 6 years ago I was 11 and still hadn't figured out Squad Command yet, but it's not difficult now.