Update 2015-10-23: The latest release of El Capitan 10.11.1 that was released yesterday fixes the auvaltool. It seems like a lot of other plugin manufacturers had the same problems as well.
Unfortunately one of my favourite plugins, RC-24 by Native Instruments, does not validate in the new auvaltool that comes with El Capitan. This does not only apply to the Reverb Classics bundle, but to many plugins in NI’s portfolio. The recommended “solution” from NI is a hack by a forum member which simply is finding an older version of auvaltool and replace the new one. I find it very strange that NI or anyone else didn’t notice this in the developer test releases of El Capitan.
RC-24 is a faithful recreation of the Lexicon 224 digital reverb, the only reverb I use.