I am returned in act 1, trying to get myself all random notes. I have collected most of them, i lack only 3. But the more i collect, the harder it is for bookcases to drop them... I have been struggling for hours, in excessive raids through the occultists' lair (the one with the big, bad boss with badass dagger drop), which has 5 bookcases and still, not even 1 damned note...

Should i switch over to warden's living quarters, instead? Should i keep doing runs down there? Is my assumption correct (the more notes you get, the less new ones of the remaining ones drop)?

Hmmm strange, thanks for the tip. Although at least 1 out of 3 of the ones i need, dropped from bookcase on another character of mine.