This makes no sense. Gravity has chosen to lock the items of a CLASS to that single class, meanwhile, assassins can trade their poison drug bottles. I honestly think this was some farfetched mistake that they FORGOT about. Nothing about these items shouts "oh my god exploit!" and it could become a trading currency for people to use, as they are necessary buffs for a dragon knight to take advantage of.
It's a very simple ask, with only benefits in mind. Allow players to trade these. They're locked for NO REASON.
Thank you for reading.