Everything drops frames while playing FFXIV

Hello everyone,
I hope you guys can help me out with a problem I've been having for quite some time now. So pretty much I don't have problems with FFXIV itself cause it runs without problems however whenever I'm playing it everything except the game begins to lag for some weird reason. Once I tab out of the game though everything else like my Browser, Youtube etc. runs smoothly again but once I tab back into the game it all starts to drop frames again as if FF is sucking all the performance from my pc into the game.

EDIT: Turns out after further investigation this problem only arises when I'm using Direct X11 but not with 9 which makes me worried since Direct X9 support will be disabled with the release of Shadowbringers.
Anyone know why that might be the case?

Hope somebody out there can help me out because it's really annoying if I want to watch a video or something while playing the game and this is a problem I did not have before.

Good Day/Evening to everyone :)

My Specs
GPU: GTX 1060 6GB
CPU: i5-8400
RAM: 16GB

Good afternoon and thank you for posting in the Final Fantasy XIV Technical Support Forums .

How long have you been having this issue? Where there any updates made to the graphical settings of the PC? Could you provide system report?
Simply go to the 'Config' option on the Final Fantasy XIV launcher and to the right of 'System Information' click on 'Display.' What have you tried to alleviate the issue?

Hope to see you online!

roll back to 399.24 and install this https://www.youtube.com/watch?v=offcMVAabLI required exe https://wj32.org/wp/software/empty-standby-list/, disable Hyper V and Virtualization on BIOS and W10