I think LTT, the leader of the AS and the one in charge of the whole damn war effort would know better than anyone how compulsion works and what Graendal could do. I mean it was LTT that told Nynaeve how to unravel compulsion in the first place. I would most certainly consider him to be an "expert witness". Certainly he knows better than Nynaeve.

Infact, I have often suspected that the reason a way to heal stilling was not discovered in the AoL, was because no one really tried all that hard.

Consider, who were the ones who got severed in the AoL. Criminals who committed severe crimes and refused to be bound in the binding rod. Why would an AS highly skilled in healing spend time and effort trying to reverse that, when she could rather spend her efforts healing the truly innocent sick. Given that they knew a lot more about ter'angreal and their training was better. I doubt accidental severings happened all that often, if at all. So essentially, if you got severed, you deserved it, and no one was going to waste their time looking for a way to heal you.

That might have changed in the war of power. But again it seems likely that if you got severed in a battle, the opposing channeler probably killed you instantly afterwards. With ways to heal mental illnesses(compulsion used properly), and advanced tech (shocklances), even a severed channeler was a potential threat afterall. Better to kill him quickly once he was unable to defend himself.

So it seems likely that even then, severed channelers did not happen all that often. And there would have been a LOT of injuries among the population, injuries that desperately needed the restorers. Would it really make sense to dedicate resources to researching something that would not be all THAT usefull in such a situation, when that research would mean taking restorers away from their other duties and letting potentially thousands of people (soldiers and civilians) die.

So I suspect that if the AoL restorers had truly put their heads together and researched the matter thoroughly, they would have found a way to do what Nynaeve did. It did not seem all THAT complex afterall. But as they say, necessity is the mother of invention, and in the AoL the necessacity was not there. So essentially Nynaeves discovery, while cool, does not in any way make her superiour/better to the far more skilled and experienced AoL restorers.

I do believe however that what happened to Graendals victims is something that was researched thoroughly. It seems probable that Graendals victims were mostly high ranking people with important skills and such, and healing them would have been important to the war effort. Becoming a braindead zombie was probably very terrifying aswell, more so than just being killed I would say. So from that perspective, it seems likely that it was studied. And compulsion was well understood by all, since it was used regularly to heal mental illnesses. And yet, despite all of that, the damage done by Graendal was irreversible, even to people who know MUCH more than Nynaeve. And LTT would have been there, reading the reports from those restorers.

So essentially, when LTT says that there is nothing that can be done, with the experience of tens or hundreds of AoL restorers backing him up, I choose to believe that he was right. What happened to the innocents that Graendal took was tragic, but they were most likely beyond help.

And what about the others?

By driving Graendal off, even when he had the chance to kill her, would that not make Rand indirectly responsible for every victim of Graendals in the future.

Hundreds of healthy people would be captured and mind-raped to get Graendal new pets and servants. People that would otherwise have continued to live normal lives. Do you think their families would be happy that Rand made it possible for their loved ones to be mindraped and destroyed, in order to save a group of zombies who had a VERY low chance of recovery?

And what about the chaos Graendal would continue to cause? The damage to society she would bring. Order and Belief bring strength. What happened in Arad Doman is a good example of the utter devastation that Graendal is capable of doing with her subtle manipulations.

What if letting Graendal go here just to save the drones ended up losing Rand the fight entirely? What if in retaliation, Graendal had Min assassinated to fullfill Moridins command about bringing Rand pain, driving him so badly insane that not even the revelation he had at the end would have fixed him?

I don't think there was an absolutely perfect solution here. But Rand chose the best one available. The one that he knew would achieve the most good in the long run.