It is an exaggeration to say that before the jr. pieces that those legendary weapons would be on the prize list every time, they simply were not that common to appear every time someone complete a heroic level of a boatyard.
You said yourself that you just
became strong enough to do them so you would not have any knowledge of what the drop rate was before the addition of the jr. pieces.
I do not know if they are still in game as complete items you can win in the boat yards, but with the jr. pieces you have a better chance of getting one than farming boatyards over and over.
I also just noticed that your account was created yesterday so either you are on an alt or you play DDTank on another web site. If you play on another web site please go to that website for help. This is AGE DDTank and has nothing to do with other versions.
If you are posting on an alt then feel free to post on your main. Don't worry, we don't bite.