I agree, i have fps spikes like crazy aswell. on the top end its 200+ and at the low end its 50. And its pretty frustrating. I have a great setup aswell. And sure if u dont want fps spikes you should set the fps limiter on. But honestly if it gets below 60 while having 8gb of vram. Is pretty ridicilouse. Destiny now is capped at 2,5gb vram at max graphic i think so basicly with 3gb of vram u get the same result as with you're 2080ti.
Again a simple fix if Bungie just did a passover and optimized D2 for PC. The game literally refuses to request more resources from my GPU and or CPU at any graphical level. There is 0 reason I should be experiencing the same FPS in 720p low graphics as I do at 1440p max graphics. It's ridiculous.