http://bugs.winehq.org/show_bug.cgi?id=31071
--- Comment #67 from util0002@gmail.com 2012-07-23 20:51:04 CDT --- I can confirm that reverting the aforementioned commit in the current git version solve the problem (with my Nvidia 9400M G), It actually solves it not only for Luna's aura, but also for Mortred's critic animation and blade, Lina's flaming hands, Invoker's orbs and lots of other effects that were previously overbright but not game breaking.
I tested the game a bit and didn't see anything break due to the commit removal.