Buckler isn’t very useful because you can run out of stamina very fast and it doesn’t cover enough area to be good against arrows. It also doesn’t seem to cover large area while it takes a large portion of your field of view while blocking. However, there is a way to make it more useful in terms of being attack shield.
I noticed that when you play with a buckler (if you use flail) you gain an option to attack with your shield, instead of a regular shield bash. My proposition - and given the fact that a buckler is intended to be very offensive shield - is to increase the usefulness of it by adding separate key for this particular shield setup.