Tralosk speaks the truth. Exactly as much morale will be lost as can be. The rest will remain.

when everything is decided in 20-40 days, it's quite difficult to max out five full resists...

Why full? An advanced resist is already above 50%. And an expert resist exceeds 70%. I'm not counting cloaks, as they may not be available. But if they are, then it's even higher.

Now tell me, will you risk it and spend a turn with a powerful Haven mage, trying to cast hypnosis/berserk on a unit with a resist above 50%? I won't. It's better to focus on creation: teleport or something else. Or berserk on the same ifrits.