Finding out it was Graendal was so pointless. She had no interesting reason to kill him, there was no reason to keep it a secret for so long or have it be such a memorable scene. The whole thing was all setup with absolutely no payoff. At least give us a reason to care that it was Graendal, RJ, given that you made such a big deal of it (and yes, RJ did make a big deal of it. You can argue that it was the readers who blew it all out of proportion, but that was the result of RJ writing it/setting it up that way. If the solution didn't matter, why make a mystery in the first place?). Instead, we're left with a "oh, by the way, it was this character whose name I might as well have drawn out of a hat." It's such BS. He might as well have just revealed that it was Graendal in the actual death scene itself, or had her mention it in LOC rather than jerking our chains for 8 books.