Consistent latency spikes making game unplayable

Continuing to have the same problem this league as the previous 3 leagues. Every 4-5 seconds latency will spike to 500-1000ms and then return to normal. Seems to increase in frequency during maps with large amounts of enemies, but happens even in hideout or in fully cleared zones. Have to play on predictive networking or else character freezing makes game completely unplayable.

Tried connecting to different servers (US East/Central/West/Europe/etc.) and all have the same problem. Tried different graphic settings (DX11/12/Vulcan, everything maxed/everything turned to low). Used a VPN to connect to via different locations. Ran WinMTR but nothing conclusive. Tried wifi & ethernet. Literally nothing works.

It's frustrating during campaign & early mapping because of the zorping & random deaths. Makes late game unplayable due to dying constantly from mobs/spells that I've moved out of/away from on my screen but not according to the server. Bricking maps, failing boss encounters, etc.

I play 10-15 other multiplayer games of different genres (FPS, RTS, MMO, racing) and don't experience this latency problem in any other game.