Removing the tomes is bad - groups stop forming.
Splitting the story people into separate DF is bad - groups stop forming.

Take GW2 as an example - I wonder how many people never completed the story because of Arah? Progression and story are the same thing in an RPG.

Idea: Award more tomes when the group or a member of it watches all cutscenes.

If uber fast CM takes 30 mins with skipping and awards 100, and full-on story cutscene bonanza takes 60 mins, award 200 tomes. The farmers still get rewarded proportionally to their time, story dudes still get their story, and new 50s get some extra tomes which would help them gear for AK, etc etc.