I'm not sure if it's noteworthy, but I backported gcc-4.8 to wheezy rather than installing directly from jessie/sid, since we're using wheezy as a stable base internally. I'll continue to try different things and see if there is any change here.
What is your grub version ?
Please could you gunzip kernel image and send "readelf -l filename".
The problem might be too big kernel, which can be handled only by
grub2 2.00-13 and above. See #699002,
http://bzr.savannah.gnu.org/lh/grub/trunk/grub/revision/4556/grub-core/loader/i386/bsd.c#grub-core/loader/i386/bsd.c
Cheers
Petr