One of the benchmarks showing multiplayer performance shows the AMD FX 8350 doing 'OK' when paired with a GTX 780 but when paired with a 290X performance is terrible. We're talking 20 fps less. Don't know how accurate the benchmarks are but there's definitely something odd going on.
http://m.pclab.pl/art55318-4.html
http://m.pclab.pl/art55318-4.html