I'd agree with you, were it not for the fact that I've missed stuns on Diabolos just as I've missed turning around for Baleful Gaze because the system message appears too late during combat.
That's why I suggested a lower success rate for player casting. Also, with a long enough recast timer, you wouldnt have to worry about someone spamming the spell too quickly. So unless you have a party full of RMD's I don't think it would be much of a problem. Like I said, 10 seconds is long enough to make it or break it (no pun intended) only if the spell is used tactically. Using it right at the beginning of a fight on a fresh mob would be pointless. Using it more like a stun or a chance to give healers to cure a badly wounded tank would be much more effective.