I still don't see it, Fidd. You are looking to deeply into the love thing when what you stated wasn't really established. Esdeath's love for Tatsumi is just a tool for creating a harem-like situation, it isn't anything more deeper than that. It's described as an animal instict by PM that the majority of humanity have, which Esdeath clearly accepts as a solid reasoning. And that's it. You can clearly see that she has no intention of keeping him if she is rejected. She even goes as far to sentence him to death for rejection. Her love for Tatsumi is just simple lust.
And like I said, her driving force is that of a warrior's. On a battlefield, all you can do is kill or be killed. That's all there it is to it. She doesn't have a disregard for humanity as much as you think she is, given that she gives Suu the honor of having him die a warrior's death and be acknowledged as human. Her sadism is just a quirk, nothing much. There's no actual depth to it. She just loves torturing people. That's been pretty much established.
I might have gone too far when I said she's shitty, considering she isn't really different from any other AgK character other than a handful of them which I'd say are Kurome, Seryu, Syura, Tatsumi and well, possibly Suu.
As for the Sasuke thing, I can't really grasp the full reasoning behind your statements. It's true that, in the past, Sasuke didn't quite understand the weights of his actions and snapped a few times. Don't get me wrong, Sasuke is insane to a level, but not overly insane. Seryu is what I would call overly insane, not really Sasuke.
He developed and he seems to have grasped the workings of the shinobi world just fine, because his current reasoning is pretty spot on. He will continue on with Itachi's wishes, but not exactly in Itachi's ways. If he gives them a common enemy, the villages will re-unite just like they did against Akatsuki and Madara because of the growing fear of getting annihilated by Sasuke otherwise even though Sasuke won't really try to annihilate them.
Like I said, his motives are pretty clear to us, the readers. Nor is he overly insane. I don't really think that the meh tier description applies to him.
Sasuke's character isn't amazing.
In comparison to the most of the cast, including Itachi? He is indeed amazing.