Really nice research for the project and documentation. You have some really nice and strong poses in there! I would suggest a couple of changes to make it even better. I saw your comment about having to adapt to gameplay animation and having to sacrifice a bit in animation. There are a couple of things you can still do to try and push it even further. For example, during your idle, I feel like everything is moving a lot. The shoulders come down too much and the chest bends a lot. Also, your knee keeps popping, I'm sure reducing the overall movement will help you out with that.
For the turns, I would just look to one side so you can spend a bit more time in there with the chest steady, right now feels like a spring more than an actual chest. I would also suggest using more angles involved in your head rotation. Right now you are only using Rx or Ry (depending on the software) and I would involve all three axes, creating a bit of an arch, just a bit, doesn't have to be super obvious. We usually say, just so you can feel it, not see it. Right now the head leads the motion on the turn but afterwards, the chest comes back before the head and I would suggest the head leading.
For when he is checking the shield looks pretty good, I would add some follow through motion as you hit a pose and stick there, hit another pose, stay there and so on, but I love how you involve the chest back a bit so the shield feels heavy. Same note with his head rotation, I would involve the other axes in there. Every rotation we do involves all axes except elbows, knees, fingers and those kind of straighter joints.
When he goes down to cover behind the shield, I like how he adjusts his screen left foot, but you are also sliding the screen right which would be very hard to do while you have your other foot in the air. Nice touch putting the hand on the side of the shield.
When he gets hit, I would add some offset between body and feet, leaving them behind and would add some frames on the fly back. When he gets up, would be nice to try and track his shoulders to the ground closer, so they are on the ground.