I imagine that neither of them would be able to shake off the spell [I]immediately[/I], at least, since it does have such a relatively difficult-to-define effect. Realizing how one was manipulated through sheer self-analysis and the powers of observation would probably be a challenge, so I imagine that the most Ixion - who seems to rely a great deal on such - would be likely to accomplish was to act in spite of the magic rather than simply resist it, which would in effect mean that he would experience the consequential discomfort you described earlier when doing so. Morgan, though... he wouldn't be able to figure out how he was being affected simply by being affected, but ironically he would be able to tell through sensing the changes wrought by the spell in others near him, in this case Ixion. Once he had seen how Ixion's flow of energy had changed, he would probably be able to figure out that the spell was liable to have had the same effect on himself, and subsequently make an effort to resist it.

You might do that, though mostly I'll try to be as accommodating as possible, obviously. There just are some quirks to certain kinds of more complex magic, such as that which affects minds directly, that make them a bit less intuitive. You want to blow something up? No problem, there's loads of spells that do that. But if you have a spell with a very specific effect, or one that manipulates things in a very delicate manner, go ahead and ask if you're in doubt.