Before discussing how it could/should/would be changed, in my opinion, it would be good to establish why the current method is a problem.
Is it a problem just because finding the book you want takes forever? Probably not.
Is it a problem just because guilds can rot the class tomes on even their first Turruj kill? Again, probably not.
Is it a problem because it's a waste of time and loot? Still no.
So why is it really a problem? In my opinion, it is a problem because some classes are being balanced around their class tomes, and those few class tomes are just as likely to drop as the a) unimplemented or b) silly fun effect, tomes.
If class tomes were not being used to balance classes, I would say stick with the current method. However, since they are, it seems extremely unfair for a class to need a roughly 1 in 45 drop from a few specific monsters just to match the progression that other classes are making with gear which is more common.
So yeah, in other words, I guess I agree with Tier and would like to see this be different in some way.