Well, setting a resolution scaling over 100(%) is the same as artificially inducing SMAA, which is really taxing on the entire system, especially the GPU's memory bus.
An OC on the GPU might help things keep up, but with architectures this finely tuned, I don't think you'll get much of a real world benefit from an overclock unless you get a magical flying rainbow unicorn GPU that goes to like 2500mhz+ on the core or something on air.
An OC on the CPU, however, would help a bit more. Like most MMO's, regardless of API, single core performance is still pretty important, at least to processing the incoming information from the server, and clock speed scales single core performance pretty linearly until instability prevails. It's like running my i5 4460 at 3.8ghz versus 3.2ghz. I had mad FPS gains all across the board, and up to an extra 40% decrease in frame times in really heavy MMO's like Planetside 2 and TERA and BnS. I undid the overclock because I'm technically still under Intel warranty, and now I can't overclock it anymore. Derp.
Turning off framerate smoothing, vsync, and some extraneous windows services can give you back some fpses too.
I agree with burgessanthony. Dropping the resolution scaling is usually an attempt to drop VRAM usage, and not much else (the only thing it really affects from my testing, anyway). You'd get a bigger change turning off foliage or shadows or fog volume individually versus dropping the resolution scaling, and if you're that worried about VRAM usage, dropping the anti-aliasing settings or turning them off entirely will give you back more free VRAM than resolution scaling. Resolution scaling is typically a last-ditch effort for extra framerates with not much benefit and lots of drawbacks.
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