The PC should be able to command his demons to attack himself (maybe), and should definitely maybe be able to cast attacks on himself. The main reason I want this is because I really like how powerful Twilight is (agony/vigor siphon/light dart spam anyone?), but getting yourself to below 50% hp is insanely risky for a squishy caster because it means being in the line of fire of enemies! But I guess that's why Twilight is so good. I don't know I feel kinda iffy on allowing self-targeting just for this reason but yea Twilight is good.
Speaking of light attacks, light dart is insanely good even with 4 agility the entire game. It's practically a smite-targeted spell, and if you line up 2+ enemies you have a negligible chance of missing. It's 70 power/20 sp/no cooldown/pseudo-smite-targeted; compare against humble and punish which are 70/55? power and ~15-20 sp? with a light cooldown AND conditional usage (>50% hp or made an attack last turn, respectively). I don't know, I'm just not seeing the benefit of using humble/punish over light dart in general; the only situations you'd might use them (assuming you met the other conditions in the first place!) would be single targets with 4 agility. Because of all this, I think the other light attacks should be buffed, or nerf (please don't) light dart.
Speaking of dark attacks, agony is really good when you can use it, but it essentially has two separate cooldowns: the dark cooldown which affects other light/dark abilities (I guess to prevent applying agony to an entire pack quickly), and then waiting for the agony status to disappear. I like the mechanic of it, but it just feels like it has too many barriers to use (2 cooldowns + 20 sp). I don't really think it needs to be changed but it just feels a little awkward when paired with cull (which also has a dark cooldown) on the faithful heart relic.