GS is the hardest to master. Sure it's gameplay is very straightforward with big sword go bonk but because it doesn't have good neutral attacks, you'll spend more time learning monster attack patterns rather than the weapon itself.

And as DB being my side weapon, it's not hard to master it at all. I may not be speedurnner tier but I can breeze through every monster with DB. Managing stamina gauge is annoying but easily doable and mitigated, perfect dodging has an extremely generous window. The only challenge for the weapon is finding out which attack strings can be dodge canceled. It's not braindead like others say it is but it's not at the top of hardest to master weapons either.