In my limited experience of chasing magi around, it's actually pretty bitchy to put down a mage/hybrid and keep him from lesser healing. I def think channeling should be canceled by hits as much as it is. You don't want mages tanking and charging spells, trust me. You'd have like EQ bomb paladins n shite.
Other than that, I don't think I agree that psyche should raw cancel a spell w/ no input. It's kind of bizarre. If you made it so that you had to target slightly longer or something per the level of psyche, that would make more sense. Like your int v their psyche battle, but just that your psyche quashes out a spell is mad weird. MAHAHA UR MAGIC DOESN'T AFFECT ME!! If you're gonna go there, you should be able to spec your psyche to a point where you are immune to low end/spammy magic.
I agree w/ stuff like rng chance to dismount on hits, maybe rng chance (v low at max spec) for a spell to fizzle even if everything was done perfectly, but I can't really see how psyche could impact that without such a system already in place.