I only made it, because of the claims that this algo is GPU resistant. Well... it is not and probably no matter what kind of algo they come out with, GPU will always have slight advantage over CPU. Simply because, it is better in parallel computations. And if you make single hash calculation very expensive so that it has hard times running on GPU, then even CPUs will struggle, not to mention older PCs with slower CPUs - that would render wallet not being useful anymore.
GTX 980 Ti uses 200W (at wall) to produce ~1.3 kH/s. CPU using same power produces ~0.4 kH/s. GPU is therefore approx 3 times more efficient.
Well my miner hashes at ~600H/s with E5-1650v3 @ 115W, that is pretty close to your efficiency.
I'm not sure, all I know is that I want to get paid for the countless hours that went into optimizing the miner.