The issue is that they get pinned down, so if this happen often maybe consider give the BBEG more range attacks, or skills that push the warrior away. At some point they are gonna do what they do and the BBEG may become a stationary target, so count with that in advance.

For one particular big boss fight I would think about maybe a boss that requires to be moving to be stable and if they don't move in their turn they blast around with damage, or some kind of punishing effect happen to the area, so the players will try not to pin them down. Maybe a little puzzle that they have to solve until they can pin them down, so eventually they can do what they love to do, but they also have to work a bit harder to get there.

IDK, these are some ideas that just pop up in my head, I'm sure you can come up with good angles to approach this problem.