This is known issue on LIVE server.. I started noticing this problem in Asylum hardmode, i started a trial with great fps, before fight 80-90fps, in fight never droped under 40 fps, and after 4-5 wipes, i get 50-60 fps before fight, and in fight 23-30 fps max (which is unplayeble).. For me there was 2 fixes, one log out to character menu and login again (reload ui doesnt help, or even disabling ALL addons), or restarting trial.. So i was so happy about multicore support on PTS, and i thought it will fix my issue, but sadly not.. FPS is great, but after some time FPS just drops even more then before, in fight Z'maja+1 i get 50fps, and after 5-6 tries it drops to 25-30 fps...
CPU:Ryzen 5 1500x
8Gb ram
Windows 10
CPU:Ryzen 5 1500x
8Gb ram
Windows 10