I'm not really sure where in the DD title he started working on Batman as well, but yeah I can agree with that the run feels different now than what it did when he started out. I don't necessary think it's a bad thing though.
So far each volume (including vol 4) has been 10 issues each. If they also collect DR then that makes it 20 to go. My bet would be a 6 volume run to keep the books equal in size, but that's just my guess.
Oh yeah, that would be a nice thing to throw in there as well.