Mid 2014 MacBook Pro throttling

Hello, thanks for taking the time! 

Summary: CPU and GPU drastically throttle with a little graphic load - not overheating.

This issue has been increasing over the year and neither upgrading to Mojave nor a fresh factory reset helped as I'd hoped.

Basically, whenever graphic load comes on, the CPU and GPU will randomly throttle down drastically. The most extreme is when starting a game like World of Warcraft (graphics settings don't seem to make any difference). But it also happens when just using Photoshop. Once throttled down, I have to close the laptop and let it sleep for about 2 - 5 minutes and it will be back to normal.

 I originally thought it was related to having my 4k screen attached, as that makes the issue worse, but with recent testing I realise it now happens even without the extra screen. 

It has progressed slowly worse since the beginning of 2018. I used to be able to run World of Warcraft fine as recently as august 2018 even on my external display, but by late September it became pretty much unusable. However it still worked reliably when the display was not attached, though sometimes it would throttle a little. Now however, the CPU and GPU tank as soon as the game launches. I have attached a screenshot of Intel Power Gadget that shows the drop just as it starts rendering with the game engine. 

Photoshop also suffers with the external display attached, but it seems it still works well without the display attached. The throttling doesn’t happen so fast and so severely, but arbitrarily it might start to throttle down little bits at a time, within roughly an hour of working.

It doesn’t seem to have anything to do with temperature, as it’s happened when it’s running no hotter than 70 - 75 C, and to my knowledge it should not throttle until it reaches nearly 100 C.

This is driving me crazy. It seems like a software problem but I updated to Mojave without luck, and then factory reset my computer with still no luck. So maybe it’s hardware - Any ideas? 

Retina, 15-Inch, Mid 2014

2.5 GHz Intel Core i7

16 GB 1600 MHz DDR3

NVIDIA GeForce GT 750M 2048 MB

Intel Iris Pro 1536 MB

Attached photo shows the clock speed drop that happens as soon as I get in game in World of Warcraft. 

Thank you!