I have gone back to the RIP Batman issues.
Bruce did not drug himself. It seems we are meant to understand this, even with Morrison's disjointed(but talented) narrative.
We have never been told that Alfred, Robin, or Nightwing have seen him wig out.
Someone else programmed the 3 batmen in 673-675, and they awoke memories in Bruce about Hurt's actions in mind-scrwing all of them.
And Zur-en-arrh ssems to have awakened a defense mechanism in Bruce to reclaim some elemental and basic part of himself. A reaction AGAINST something, like the person that filled him with the drugs.
Bruce as BG does not seem to make sense from the past 6-8 issues.
Or maybe it does. But, what is so significant now that would make Bruce crack?