Maybe the API test is influenced a lot by the GPU. Like i said, with the R5 1600 @ 3.7GHz all core, i got 2.6M in DX11 MT and that was Optimized default with the Ripjaws running at 2400MHz Cl16. ST is same as yours.
But in Firestrike both my R7 and R5 lost between 4-5K in Physics scores.
I used to get this much with the R5 . . .
At 4GHz on the R7, i used to get over 20K, now . . .
But my games are not affected as well as other benchmarks. Just 3DMark.