Sure thing!
I cropped out a few shots and noticed most of the problem is in the spine and shoulders. A lot of characters will have a rigid back with the stomach exposed when the spine should be relaxed, like when sitting.
So for the first shot a resuscitated character is sitting up. The spine is pulled back and the chest points out and upwards, making the shoulders draw back. The spine should be curved in more of a C shape, with the chest pointing slightly downwards and the shoulders hunched to give the illusion that he's propping his body weight on them.
The second shot is the hands over the lip of the pool. Because they aren't level with the top of the lip, it makes his hands look dead =]
The third shot is mostly the back. It's very rigid, but the s shape should be much more subtle. This would cause his chest the point straight(instead of curved up) and soften his shoulders.
The fourth shot is extremely rigid. He's at nearly a 90 degree angle with his spine curved outward and his shoulders straight. Nobody sits in bed with their laptop like this. The upper half of his spine should be pulled toward the laptop (or else his neck is really gonna hurts)
The fifth is an example of something more subtle but more common in a lot of shots. Some parts of his body match different body language than others. so for this one, we have a character acting aggressive and moving towards another, pointing a finger. His arm is engaged towards the character, but his body is stretched away from him. He's gettin all up in someone's grill but the only thing on him that shows aggression is an arm and his face. There are other shots where when a character is in some type of action or movement pose, only part of the body is engaged in the action while the rest isn't.
I'm not a figure expert(whatever that means), but I've used model poses for references before so hopefully loosening the spine will correct the shoulders n stuff. If it was drawn, that'd be different, but because it's in 3d, the posing is way more noticeable.
As for artwork, it doesn't matter how messy it looks as long as you make in intentional. After all, that's what style is. My hand makes it nearly impossible to get clean linework, so I just embrace the messyness out of convenience and just roll with it. Visuals are just as important in a comic as the writing. Readers want to be shown stuff. The artwork doesn't have to be a masterpiece, it just has to be able to convey important visual information like gesture and expression. Having models seems to limit the amount, detail, and variation of expressions and gestures, making the models feel like robots.
I still think you should use the renders in some way because you have a lot of visually engaging shots. I've been using a program like this (I think?) to get better pose references and I'll probably be using this method for my comic in the future.
Okay I've tried to post this twice, hopefully it will success or someting I guess