Hi guys, I found a solution!!!
the Steam update modified the rocksmith app to run only by running steam (open steam://run/221680). If you try to launch directly from Steam/steamapps/common/Rocksmith2014/Rocksmith2014.app will get a crash report. Only works from Steam or from your Applications (open steam://run/221680).
RSInjector works launching Steam/steamapps/common/Rocksmith2014/Rocksmith2014.app with an environment variable DYLD_INSERT_LIBRARIES to insert RSBypass.dylib. Beacuse the app can´t be launched from Steam/steamapps/common/Rocksmith2014/Rocksmith2014.app directly, then RSInjector will fail.
I patched my Steam/steamapps/common/Rocksmith2014/Rocksmith2014.app to insert the RSBypass.dylib directly to the Rocksmith2014.app. So, now I just run steam and play rocksmith from steam without RSInjector and works with DLCs.
I download RSInjector code, compiled RSBypass.dylib with xcode using i386 architecture, this is important because Steam/steamapps/common/Rocksmith2014/Rocksmith2014.app is i386 architecture.
I download insert_dylib app from https://github.com/Tyilo/insert_dylib, compiled with xcode. Run insert_dylib RSBypass.dylib Steam/steamapps/common/Rocksmith2014/Rocksmith2014.app/Content/MacOS/Rocksmith2014 Steam/steamapps/common/Rocksmith2014/Rocksmith2014.app/Content/MacOS/Rocksmith2014new. then rename the Steam/steamapps/common/Rocksmith2014/Rocksmith2014.app/Content/MacOS/Rocksmith2014new to Steam/steamapps/common/Rocksmith2014/Rocksmith2014.app/Content/MacOS/Rocksmith2014
then I run Rocksmith from steam without RSInjector and works with DLC because the executable is already patched.
Beacuse I know that you may not have xcode I uploaded my patched version, So follow the steps:
1) open finder and go to your Steam folder, Steam/steamapps/common/Rocksmith2014/
2) rename Rocksmith2014.app to Rocksmith2014.app.old
3) download my patched version from https://drive.google.com/open?id=0By6BGVp__jafUjkxOGlUdGIyUWM
4) unzip and copy my Rocksmith2014.app to Steam/steamapps/common/Rocksmith2014/
you should have two Rocksmith2014 (my Rocksmith2014.app and Rocksmith2014.app.old)
5) double click over Rocksmith2014.app it will alert that it was download from internet bla bla bla, just click open. Then it will crash (because was not lauched by steam), just ignore.
6) Open Steam, clink on "play Rocksmith2014"
7) enjoy your DLCs :)
You my also remove the quarantine atribute from Rocksmith2014.app. It should removed with the alert message that said that it was download from internet, but if not you can remove the attribute with:
xattr -d com.apple.quarantine Steam/steamapps/common/Rocksmith2014/Rocksmith2014.app
Note I always use Steam/steamapps/common/Rocksmith2014/, You shoud look your Steam app folder where steamapps/common/Rocksmith2014 is in there.
If Steam update Rocksmith again we will need to do the insert_dylib again.