I am aware that novels are not a foundation for game design. But they tend to give an insight as how the world we are playing in usally is thought to be. I am not saying it HAS to be that way. Every author has his or her own look at things, be it game, book or movie. I am not sure why powerful characters are such a problem for some. The adversaries and stories just need to be tailored around that. Not easy i guess. I have always had more problems designing advertures for higher level characters since the options they have grow. And talking about reasonable in a fantasy game is strange anyway. But i guess you are mainly talking about game blalance and i agree with you there.

About comparing apples and oranges, i don't really think it is. Sleep and Hold are both designed to take a creature out of combat most of the times. Looking at it logically BOTH would need concentration. Hold to fight against the resistance of the victim and sleep to keep the minds of the vichtims from awakening due to external influence like
noise.
I think if i go through the spell list there would be more spells where you ask yourself that exact question. Why does shield of faith reqiure concentration but spiritual weapon does not? Blur requires concentration, Mirror Image does not. I do not see logic or consistency behind that. Not much at least. Since it is all thought up you can always come up with an explanation.

Apart from logical explanations for why or why not i created this thread because it was something that i disliked every playthrough i did. Not the mechanic in itself but the way the game handles it. It feels awkward. Too many times where i was better off not using concentration spells because it was wasted effort. You can move and attack. So if i move my caster into a position where i hope he will not get hit an NPC either moves to hit anyway or throws grease or something else in the general direction. And that usually suffices to break the concentration. And often enough in the same turn so that the effect is wasted completely.

For me that is not much fun and that is why i think something should be done to mitigate this. At least somewhat but since this is still VeryEA we will see where it is going.