I just finished reading the Russian novel "Lena Squatter and the Paragon of Vengeance" by SF author Leonid Kaganov. It's not exactly a Harry Potter fanfic, but it's very similar to MOR in that it tries to present an explicitly rationalist hero, and IMO Kaganov has handled the task better than Eliezer.

The protagonist is an unattractive and immoral woman whose only strength is extra rationality, which she applies to the sordid and corrupt world of Moscow corporate politics. Using the familiar LW intellectual ammunition - from Pascal's Wager to evolutionary psychology - she gets people fired for talking back to her, gives and takes bribes, blatantly manipulates men (driving one to attempted suicide), and then in the end when she's found the perfect boyfriend her plans neatly backfire, forcing her to kill him and then herself. Lena's exploits are shown with a lot of detail and believability, and overall the book has punched me harder than anything Eliezer wrote. Unfortunately it's unlikely that it will ever be translated into English.