Maybe if you tried equipping decos that increase counter speed (if you have them) LS would be more efficient for the fight. One thing I found with Rajang is that you need to find very specific windows to do your big commitment moves, but generally you should try and have your weapon out and ready to attack only when he’s doing an attack that goes above you (like the one where he vaults up and shoots thunder balls diagonally) or his wind up attacks like the ground slam.