Just out of curiosity... is your CPU usage high now that you've upgraded ?
I'm using Phoenix 1.5, so i got 100% on single core even when i used 11.6.
No difference after updating to 11.7.
So, even though i didn't use stable 11.7, i can say in beta 11.7 i saw no difference & jumping as mentioned in 1st post.
Try to add second miner for each card. I got no difference while using single miner.