Why are people complaining about Psychological being difficult? He's pretty powerful if you know how to play him. You want Terrify for the Schadenfreude healing (which helps a lot, trust me) and Overdrive, dealing double over-time-damage, at the cost of 10% health per turn (which is compensated by Schadenfreude) the crux of the set is Epiphany, dealing serious damage each turn. You can go Electrical Storm for the extra Focus, which give you the oppurtunity to spam Corruption for high damage and recovery. The rest is up to you.
In the missions, if the units aren't stong enough, they just make the commander immensely OP. I mean, enfeeble, stike 1, rally all bloodthirsty is pretty amazing.