Renaming the 355.11-r2 ebuild and changing the nvidia-drivers dependency slot does the trick.
Now it's 358-16 :
1535 KB 17.11.2015 20:25:00
nvidia-settings-361.18 is now available, and it depends on x11-drivers/nvidia-drivers:0/361
And another newer version:
Personally, I don't see the point in the version bump. We are already moving in the direction of dropping nvidia-settings as a standalone package #562910, so bumping a package that is effectively on its way out seems like a waste of effort. Just my 2 cents.
*** Bug 582488 has been marked as a duplicate of this bug. ***
The main reason at the moment for keeping nvidia-settings around as a standalone package is that it always installs libXNVCtrl.a whereas nvidia-drivers will only install libXNVCtrl.a if USE="static-libs".
Several packages, including sci-libs/vtk, depend on libXNVCtrl.a and only permit it to be provided through nvidia-settings. Hence, when nvidia-settings is not bumped one gets into a sticky situation with regards to unresolved dependencies.
Please use x11-drivers/nvidia-drivers[tools] instead.