I tend to agree that Batman has just as much 'writer's fiat' protection as Superman, if not more. It isn't always DC's fault though. Some Batfans (Not all, nor even the majority) are very vocal in their fandom and will not tolerate anyone out showing him. That's true for a section of any character's fandom, but since Bats has such a LARGE fandom, his extremists are in greater showing too.
I remember when Johns had Hal Jordan actually land a punch on Batman, and some batfans went NUTS about how it wasn't possible. Hal didn't knock him out, he just landed a punch, and even that was too much for some to accept. It was in Green Lantern Rebirth, Hal's own comic... he was therefore, the star of it. But cries of favoritism went up as if the title wouldn't give a clue that yea, this might be Hal's story
So I can see why some DC writers would be a bit nervous about rattling the cages in some areas.
That said, Batfans also include some truly awesome people who will happily tell you the best creative teams, relate to you lore about obscure 3rd tier villains, and be happy to introduce you the flavor of Gotham they'd think you'd like. Many of them dislike "Batgod" as much as the next reader, and what they love about Bruce include his mortality, flaws, and failures.
I'm not a Batfan myself (I prefer Nightwing) but I think for every really over the top Mary sue story he's had, he's had at least 5 awesome ones that fit very nicely indeed.