I really hate the whale-mothers. Felt like beating a dead horse and stretched my suspension of disbelief too far. When I first read the previews I held out some hope that maybe Dunyain women just ended up that way once impregnated and it was some kind of weird second-puberty, but nah, seems like they're born incubators and lack Dunyain emotional stunting and conditioning for yet another example of "Hey don't women have it bad?"
I found it disagreeable from a taste standpoint as well, but it is also flawed in that it is self-defeating and ultimately less interesting than the alternative. Consider the following: the Dunyain turned their women into axolotl tanks because they wanted total control over their bloodline for eugenics and found lobotomized baby machines the shortest path to that goal. But this is a form of self-harm - children don't stop needing maternal care at birth, they typically require many years of it before they reach maturity, and "Whale-mothers" can't give that. This means that the Dunyain's chosen path was actually destructive and subversive of their goals - they needed a way to establish control of women without removing them from the natural reproductive cycle so drastically. There was a way to do this. You will recall that Kellhus more or less effortlessly seduced Esmenet and Serwe. I see no reason that comparatively more permanent seductions could not have been carried out under controlled conditions - and Ishual is conditioned ground. This means that a more productive strategy would have been finding a way to perform on each Dunyain woman something akin to the sexual imprinting seen in the Honored Matres of the later Dune books - an experience so addictive that it essentially collapses the difference between intercourse in general and sex with a specific person into one event, making it impossible to conceive of having more than one mate. This would produce the control factor. Combined with women's natural propensity to care for their children and the general fanaticism of the Dunyain, and it would be easy to breed a sub-species of women who are totally specialized to "voluntary" breeding to the exclusion of all else: they have their children by the man they are imprinted to , and all else is unimaginable to them. Other details could be handled in a miscellaneous manner, e.g. having those turned menopausal poison themselves as the Dunyain who received the dreams from Moenghus did. This could even be promoted as a highly rational act, even "desirable" in a sense, since their ability to perform their function, motherhood, had come to an end; a controlled culture could have been created that would take it for granted that they would do this, a further reinforcement factor. Or perhaps shortened lifespan could have been designed in somehow. All of this would have gotten the eugenic job done while also providing lots of creepy feels to the audience.
And it would have made Requires Only Hate that much madder.