If you could kill off one of the scions...

[Cilia]

Just how many people do you think there are who know about the Echo? Just because we have a not-even-intimate knowledge of it (and mostly only as a result of possessing it) doesn't mean we can even remotely begin to analyze it. Similarly for all of the Scions, the Echo is still a mostly mysterious ability with many unexplained facets. No one would have even thought to link the Ascians to the Echo until very recently. It's important to remember that outside of our small group, the Scions, no one really knows anything about the Echo.

We were there and had all the knowledge and more experience than Minfilia. Fewer contacts, but more experience.

It doesn't take a genius intellect to realize the Sahagin Chief was talking about the Ascians (heavily implied to be Elidibus himself) and that whatever they gave him made said Chief rather like the Ascians. Yet, Leviathan pretty much ate said Chief. That being the case, logically it should be possible to kill an Ascian... somehow.

The rest of it is R&D done largely by Urianger and Moenbryda, respectively.

Much as I love Thancred, even I know that he is the only one responsible for his possession by Lahabrea. Much as the other Scions like to blame themselves, looking back and thinking on what they could have done better, ultimately it was Thancred who took too much upon himself while giving to everyone the impression that he was handling it all. Given his dialogue after the 2.0 endgame, it's even hinted that he likely used himself as bait and ended up falling into their trap. As for it being Minfilia's responsibility? Only on a very superficial level, and even then she acknowledges that she should have seen it coming.

Yes, Thancred was pushing himself too far and making it look like he was okay. If Minfilia were really that good of a manager, she should have been able to see through this - and she did, but did nothing about it. That is why I hold it against her. She knew he was pushing it too far, and rather than hurt Thancred's feelings and keep him grounded for a short time, she allowed him to continue overworking himself because "there's not enough people, and we're really busy..."

Is Minfilia only superficially responsible? If you frame it that way, I suppose. If you want to frame it that way she is only superficially responsible for most things the Scions achieve, though, which is what I've been saying all along. You gotta take the bad with the good.

Actually, [being overworked and understaffed] is [a valid excuse]. Thancred is his own man, he was the one who chose to put on a brave face while taking on many assignments. Also, name one manager who hasn't ever screwed up. There were a lot of things going on with you the new recruit and Primals popping up all over the place and god only knows what other investigations she had the other (minor) Scions undertake. She trusted Thancred, trusted both his strength, his skills and that he was capable of managing himself. So sure, she has to make tough decisions, but one of those tough decisions was probably to not micro-manage Thancred which, in all honesty, might have actually made him feel worse about himself.

No, it's not. Responsible adults don't make excuses.

Thancred is partially responsible, but so is Minfilia. I don't hold either of them fully responsible, and honestly, Ascian possession was an unknown factor. That said, we were told that Thancred was more vulnerable as a result of being overworked and stressed. As manager, Minfilia is in some part responsible for it - how much personally depends, but being responsible for it, she should have done something about it and did not. So should Thancred, I admit that, but if you want Minfilia's job to be manager she should know when to put her foot down. That's part of being the manager too.

She micromanaged us plenty (e.g. sending all the Archons with us on the Ramuh mission, after we had more than proved we were more than capable of resolving conflicts with minimal assistance). Why should Thancred have it any differently?

Everyone screws up - it happens all the time. When you hold the fate of the world in your hands, though, the margin for error is so small as to be nearly nonexistent. You don't get to say "Well, we were overworked and understaffed, so one of my best agents overworked himself and got possessed by a demon-man and blew up a city. I coulda stopped him, but well... we were overworked and understaffed, so it's not my fault."