So, having spent an entire session in the Diadem after Grade 4 fish (which you need 300) and not even getting a single bite - I'm wondering if the catch rate is insanely low, or it's perhaps bugged?

Yes, far as I know I was in the right spots, and the right time - with the right baits.

NOT A SINGLE BITE

I'm totally finished with Botanist. Won't take long to finish Miner, have EVERY other Land achievement but this one and now I'm wondering if it is even possible.

I actually have 3 already - but that was before the expansion dropped. They were rare then, but doable at that rate. If I remember correctly, I got all 3 of those from a single instance. I thought at the time that would be a slog, but doable.

Is it me? Did something change? Is it bugged?