I have just tried to play WoW using the latest 64 bit Mesa from git, and have
noticed that libGL refuses to load the r600_dri object, complaining that:

libGL error: dlopen /usr/local/lib64/dri/r600_dri.so failed
(/usr/local/lib64/dri/r600_dri.so: undefined symbol:
_ZTVN10__cxxabiv120__si_class_type_infoE)
libGL error: unable to load driver: r600_dri.so
libGL error: driver pointer missing
libGL error: failed to load driver: r600
libGL error: Try again with LIBGL_DEBUG=verbose for more details.

The symbol _ZTVN10__cxxabiv120__si_class_type_infoE is from libstdc++, which is
not listed as a dynamic dependency of r600_dri. Since wine64 doesn't have a
dynamic dependency on libstdc++ either, the dynamic linker does not know how to
resolve this symbol.

After I had relinked r600_dri against libstdc++, WoW-64.exe was able to run
successfully.