I can give a brief feedback on a recently upgraded PC spec.
My old rig:
i5 7400 3ghz (3.6 turbo boosted) 4core/4threads
GTX1050ti 4GB
16GB DDR4 2400 (HyperX)
Game was running on 60fps idle in mushin (fps limited to 60 and graphics on 2) optimized for combat and all that. During raids it drops to 10, but stabalizes around 20 in the long run (ctrl+f enabled ofc). Stutters yes, large fps drops, freezing and crashing never observed for 2 years since I had this config.
Current rig:
i7 9700k 3.6ghz (4.8GHz turbo boosted) 8core/8threads
GTX1070ti 8GB
16GB DDR4 2400mhz (HyperX fury) (debating on changing it right now with 3000mhz or 3200)
MSI z390 Gaming Pro MB
Game runs smoothly on graphics set to 4 on both idle and during dungeons. 120fps in idle, 85-110fps during dungeons (6man). During raids fps drops to 40 for a few seconds, then stabalizes at around 60-70 (during sb drops to 50 for the duration). Game not optimized for combat and with ctrl+f on.
I dont use bnsbuddy or any other external software for BnS. Game is installed on a 120GB Intel SATA SSD.
To conclude with the load of the game on the new rig: during gaming, single core boost goes to around 4.5-4.6GHz. Temperatures dont exceed 64C and the load of the core around 90-93%. GPU wise, the 1070ti holds pretty slow and the max load I got was around 35-40%. Temperature wise it goes to 74-75C but I notice it goes that way on every game I play anyways.
So, to conclude the said above, PC upgrade was may more valuable for bns than expected. I can play way more smooth now without any worries. If you like to upgrade your PC and you have the funds, you dont need RTX, its garbage. Get 1070ti or 1080, that should be more than enough for at least 2 more years.