I can completely understand your frustration having gone through this myself. However, those peeps that are farming the dragons are often after something other than the pally books and will likely help someone needing it for their epic than keeping it for themself to sell. Many of the folks I encountered were merely trying to see if they could indeed kill the dragons solo or in one grp or less.
I found by sitting in the zones and constantly checking for Naggy, Vox, and Talendor, enabled me to catch peeps as they were coming in for the kill. Don't bother with Gorenaire, she's so rare its nuts. Anyway, 9 times out of 10 if I asked to loot the book should it drop I was told sure and almost always invited along even if it was only to buff. Of course it didn't drop every time. But after 11 Naggy kills and 8 Vox kills I was able to get both parts of the Book of Scale.
The point is, don't give up. It's your epic and it will mean much more to you to be able to say "I did it" and not "I bought it". While the books are only a small part they are the longest and most frustrating part and a huge bottleneck for all pallies.
Just keep checking the zones.