Completely agree about Legacy Datacrons, and good news, from today's Q&A post:
Misiolak: The Datacrons are a nice addition to the game, but getting them for all the characters is simply not fun. Do you plan to include Datacron sharing in the Legacy unlocks?
Daniel: Long term we plan to move many of the game’s reward systems to be Legacy-wide and Datacrons are definitely on the list for consideration.
Hope we get them sooner than later.