It seems, like E5 2609 v3 is too slow CPU for this algo.
I've tested octane on more stable mobo with celeron CPU(Dual-core), and as you can see, graphs became even worse. But, it doesn't matter on PT algo, as it still more than 3 times faster than PC1.
Conclusion:
Octane needs fast CPU for PMC algos. That's...pretty much it. Considering purchasing i7-6800k