From what i have been reading around the web,it seems most issues with BF4 are with W8-8.1 and with BF4 in general.
One of my clanmates actually uninstalled W8 and installed W7 just to play BF3 and BF4.
Running tri fire with BF4 is a little overkill anyways.I run 2-7950's in crossfire on ultra 1920X1200 with no issues whatsoever,In fact my 6950 crossfire also ran it fine in Ultra.
What resolution are you running?
AMD Phenom II 1100t @4.0Ghz /Asus sabertooth 990fx/2x Gigabyte 3G 7950's in crossfire/500G samsung 840 ssd/16G G-Skill Ripjaw 1600/2-samsung 24" monitors 1920X1200/Corsair AX1200W psu/W7 pro 64,G19 keyboard,Roccat kone pure mouse,Cooler master HAF932,Corsair H100i water cooler,Zalman ram cooler.Sound Blaster X-Fi Titanium Fatal1ty Champion Series,Logitech Z5500 speakers,Roccat Kave 5.1 headset.