I forgot how to get ingame readings like what you posted MiRai. The main is in Boralus and my alts are in Dalaran--- beating on a turnip. I found that while dpsing it puts a realistic stress on the CPU/GPU to give a more accurate reading.
I lowered my CPU OC to 4.4ghz to match your cpu better. I removed the GPU's OC entirely.
Renderscale 100%. Slaves set to 1. DX11. Physics Interaction Player only. Main settings 10, 3440x1440p.
Here
*edit* Slaves are 20fps background and the foreground is 144fps *edit* 30 'slaves' and my main. So 31.
I then thought maybe it's some weird 21:9 vs 16:9 bug. So I messed with the renderscale and had it output @ 5120x2880 (renderscale 200% - 2560x1440, XB270HU- old monitor) . Had my girls fighting a turnip in dalaran, took my main into LFR. 45-55fps consistent. I then had my friends pull all the trash and unload AOE style~ that caused my poor little 980ti to be overwhelmed; stuttered and dropped frames (20fps).
Here
Notice how under normal WoW gameplay (first picture) my GPU doesn't really even come out of powersaving. Goes up 30w. When I changed the resolution to 5120x2880 it went to 250w.
FWIW a friend is playing 20 on a 3570k. Although he has optimised his setups to allow it to work out ok. (renderscale 0.1 on alts etc etc).