For DoL it is based on the level of what/where you are gathering. With a fudge (random) factor. At fishing 25 I get about 2X the SP in grade 4 waters than grade 3. Can't reliably find grade 4 fish schools to test on so this is open water.

As for DoH, I find levequest rewards are based on quality and durability at finish. Quality is weighted far more heavily than durability and the random factor seems to be in play but of minor influence. I believe I see a slight weighting toward quality in grinding for SPs, but the random factor here is at least as strong as any weighting, perhaps stronger.

Reika, that is a classic example on an inadequate statistical sample. You need ... IDK going to go with 500 tests and a spreadsheet minimum.