Fishing has too much RNG

[Bardo]

Given that you have godly gear, how often do you get HQ fish? For miners and botanist, max base chance is 15%. Is it something similar for fishers?

With 251 perception, I have been HQing right at around a 24% rate.
My sample size is only about 300, so it's probably not 100% accurate; however I think it's enough to say definitively that Fisher doesn't cap at 15%.

One thing that I haven't seen mentioned, but is a VERY important thing for Fisherman to understand:
Live Bait almost doubles your "bite rate" compared to using lures.

So if you're looking to pull in a lot of a specific fish (let's call it fishX) and you find a lure that only pulls in FishX, but you have a live bait that pulls in 70% FishX and 30% FishY, using the live bait will almost certainly result in more FishX catches over a specified period of time.