That is just a run of bad luck my friend, the great leader effects are hardcoded. It may be different in Conquests, but as far as the mod goes we didn't change anything there.
Sorry about the problems, I know I have gotten Great Leaders in the game. I can ask the testers when the last time they got a Great leader was. I'll let oyu know the findings, and again I am sorry for the problems.
Yes, in 1.27 the Great library should work as normal.