Just replaced my 660ti with a 780 a few days ago, and just got around to playing BF4. That been said, every chance I alt/tab, or play Windowed, I see my CPU usage is @ 100% [ Intel Ivy Bridge,i5 3570k @ 3.4ghz], based off of the intel desktop gadget. It's not full of shit either, as I'm experiencing consistent lag spikes. The only other programs running are usually chrome/Spootify.
Am I doing something wrong, or do I need to OC? I'ma dipshit in this department, so forgive my ignorance regarding the matter.
Its displaying typical CPU bottleneck behavior. though a 3570k really shouldn't be bottle-necking a card like that.
Try overclocking, if its a CPU bottleneck that will alleviate some of the problem. If you have an aftermarket cooler already, you can pretty much just set the CPU multiplier to 42 for an easy 4.2Ghz overclock. Much higher than that and you have to start manually tweaking voltages.
I assume you're playing multiplayer? Multiplayer tends to be really CPU dependant, so it isn't very surprising to find that your cpu may be pushed to its limits. Overclocking will help alleviate the problem somewhat, just be careful about it.