see summary according release information from NVidia http://us.download.nvidia.com/XFree86/Linux-x86_64/346.35/README/minimumrequirements.html Reproducible: Always
I am running xorg-server-1.17 with nvidia-drivers-346.35 without any issues.
09 Feb 2015; Jeroen Roovers <jer@gentoo.org> nvidia-drivers-304.125.ebuild, nvidia-drivers-331.113.ebuild, nvidia-drivers-340.76.ebuild, nvidia-drivers-343.36.ebuild, nvidia-drivers-346.35.ebuild: Raise x11-base/xorg-server compatibility (bug #539378 by bwcknr).