Does the weapon progression make any sense or seems a tad bit off?

My total attack damage is 192 while using a level 16 neglected Greatsword, (I’m level 43 with 20 strength), but every level 43+ Greatswords give me less total attack damage. This is the literal 2nd Greatsword I’ve picked up, and it’s better than every single Greatsword that I’ve picked up since. I’ve picked it up before blade some time after the yeti, and now I’m past the Viper boss and I’m in the next area, yet despite all the Greatswords being higher level, they all have significant lower total attack damage. Is this a possible bug or this is how the game is supposed to be?