I feel like people think a grind has to have randomness. It doesn't. I would rather be told "Do this 20 times and you'll receive a reward" instead of "Do this 20 times and you'll probably received a reward, as long as RNG doesn't screw you.". Because someone is going to find themselves doing that activity more than 20 times, and all the people who received the reward in fewer attempts aren't going to make that situation feel any better.
Like the original poster stated, they've run the same dungeon 16 times without seeing the needed drop to progress. What exactly is the magic number where we can stop saying (quote) "..Nope has nothing to do with RNG. OP just wants the weapon without putting in the effort to get it.."? and instead start agreeing that there might be a better way than basing everything on random chance?
I, for example, like what SE did with alexandrite. There are multiple ways to get it, and all involve grinding for something. You can accumulate them more quickly if you choose to toss in dumb luck (FATE drops), but you're not stuck if you don't.