Turning RnG in to a science is fine for the Forum but game play wise it's another matter.
Run Garuda for 3 weeks a hundred times, get books every single time. Not 8 classes, miss the one you want but ALL books and the RnG becomes rigged.
I farm Mahogany, base 82% and get 1 in for on a node, you obtain nothing. Hit Field Mastery II and boost it to 97% and still get a you obtain nothing on every node? I just stop hitting Field Mastery II and mash insert.

We stop trying and that's the threat of funky RnG. People stop bothering.