Welcome back!
Yes, newer content has even higher demands on your PC. It’s a curse. 
Outside of hardware changes and tweaks, you can also:
- Put your graphics settings to 1
- Enter the commands in this thread Graphics macros for better fps (Updating for new forums)
- but then set your Projected Textures back on - you need them to see the fire you’re standing in!
- Reduce your Resolution Scale. It will make your details blurrier but do wonders for your FPS. Strike the balance most comfortable for you.
- Cut your addons to the minimum.
- Reseting your UI is a nuisance, but can clear out stuff and improve performance, especially after updates https://eu.battle.net/support/en/article/7549
Oh, and if you are on the Graphics option setting DirectX 11, try the setting DirectX 11 Legacy. That sets you back, apparently, to the graphics handling before the recent patch, and helps older machines a lot.