So, Daemons and Space Marines and lots and lots of aliens tend to be immune to mind affecting psychic powers, which makes sense to a degree…
Then I look at the Daemon Bane power line in Ascension and question it a fair amount, simply because of the third power 'Word of the Emperor' where you are overcoming the enemy mind and will with the words of the emperor. By it's description its a mind vs mind effect, and thus Daemons, Chaos Space Marines, and a numerous set of aliens would be uneffected, despite the fact this is a power specifically developed to be used on Daemons and Heretics.
So my question comes down to: Is this one power just not mind affecting? Or should the Immunity to Mind Affecting powers on Space Marines/Daemons be reworded to Mind Controlling? Because I agree that you really shouldn't be able to dominate a Daemon or Space Marine, but I don't see why a power made to stun non-believers of the imperial creed doesn't actually affect them.
But powerful Daemons and other supernatural beings (including Space Marines) will usually have a high Willpower, not to mention most of those things are warp tainted, so trying certain powers on their minds by using your mind will only make you get corruption points most of the time. Just a warning. Almost always, the description in the Power will tell you this or not.