I think a lot of it has to do with the fact that he is desperately in need of a family but refuses to acknowledge it. So he surrounds himself with proteges, partners and associates -- all the Robins and their later "graduate" identities, all the Batgirls, Huntress (prior to the reboot anyway,) the original Azrael, Batwing, Catwoman, even Man-Bat and at one point Bane. When Babs was Oracle she was often the one to tell Bruce off when he fucked up. And she's also the one who eventually gets it through his skull that he has family, he has people who love him and want to help -- all he has to do is accept it and not try to do everything himself. And he, Clark and Diana are so close they're almost my OTP.

I think that brief period between The Return of Bruce Wayne and Flashpoint was Bruce at his healthiest -- he's finally accepted that he's not alone, and has taken his operation world-wide.

BTW the reason Batman takes the lead on the JL is because of his superior strategic skills. He's got very little in the way of social skills (important in a true leader) but he knows where people need to be and what they need to do to get the job done. His paranoia often gets the better of him, however -- see the "Tower of Babel" arc of JLA.

I don't think anyone is the true de facto "leader" of the League, but pretty much everyone just does what Batman, Superman and Wonder Woman tells them to.