For how large the sprites are, they're rather boring - the detail density is low. So, if they convey all the information you need to convey, then you can safely reduce the sprite size. The more zoomed-out gifs look more interesting than the 100% zoom ones because all that dead space on the sprites is reduced.
I think you should keep the 8-directional movement though. Your movement handling, with units pushing each other, looks very cool and smooth, and reducing the characters to having only 4 directional sprites would damage that smoothness a lot. 4-directional sprites are good when movement is confined to 4 directions, with free movement, you should have at least 8 directions.
Thanks for the comment!
I modelled, textured, skinned, animated and rendered the char in 3DS Max and arranged the output into a single spritesheet. This whole process including test renders took more than a week for the single character you see above. Due to a skeletal animation fault (which was my mistake) I had to redo the skinning and all the animations from scratch. It was a really painful and frustrating process.
I was originally planning to make the char size a little smaller but after trying tons of different sizes I realised that this is almost as low as I can go without having the need to edit pixels individually and not lose animation clarity. This is the first character I made for this game and I would have to revisit it further down in the development process.
I was going for a more flat shaded (cell-shaded) style. But decided to add some little bump mapping using a grayscale displacement map on the model. Do you think the char is too flat in color or does it lack the detail in its geometry and shape?
Would it have been better to use for example a single flat skin color for one arm and a darker color for the opposite arm like most do in pixel art chars? That style is much easier to apply but I think it makes chars look too flat.
Here's an alternative render for the same char with "Ink & Paint" (cluster flat render) shader in 3DS Max.
NOTE: This is not the shading used in the GIFs above.