600 from 520 in 3 days? Doesn't pass the smell test. Using DIM I just put gear on my character to make him 520, then put on a 600 power weapon and it bumped me to 530. Again, doesn't pass the smell test.
First off I read everything you typed, but it makes no damn sense. Even on my second character which was 545 two weeks ago, when I transferred 3 600 weapons over from my main it took 2 weeks of grinding to get him to 590. That's with a 600 weapon in all 3 slots. Don't tell me I don't understand internal calculations, I've been playing the game since D1 and have grinded to max power level with every bump. As far as the 'Was it fair', yes, it was fair. Does it hurt you at all? No.