That's not bad at least the Core is better on the 990X.

I would suggest using 50% LLC on CPU and no LLC on QPI. From my knowledge and experience it seems Intel architecture is designed to have fluctuations in voltage. You may be more successful with your overclock so give it a try. Also since you are running 24GB, I would mess with DRAM Ref voltages. I recently learned increasing it helps also, so try +12.5mV on all channels data & ctrl.