You're clearly very comfortable with draftsmanship and rendering! Your use of line-weight is awesome, and I am in love with the way you've drawn that hand with the buckler - it looks straight out of a 3D render, which is saying a lot.
I don't think you really need to fix anything specific in your latest pieces - the proportions have a bit of an Angel Ganev thing going on, which is fine. Areas to look into improving are mostly anatomy and the planes of the face. The construction of your noses is a bit-samey and not as confident as the rest of the drawing - make sure you review that, but you could also double-check eyelids and lips! Photo references with strong lighting will also allow you to read the planes of the face better, and put that wonderful rendering skill to good use. Eventually you'll want to start planning your global values a bit better, which is the essential skill for an easy transition to color. Great head studies, keep doing more!
As for your action piece, it's looking good so far. Motion is better suggested through exaggerations, and the way you're pushing that perspective is a fantastic example of that. Dynamic poses can feature straight elements depicted as slightly curved, for instance that sword could be displayed as a partial arc instead of a straight edge. This even applies to limbs, in some cases! Having an off-balance center of gravity and strong reliance on line of action also helps a lot. I don't think there is any need to display motion blur, so keep doing the kind of rendering you've been doing so far