I'm having the same issue plus I'm talking to a discussion thread on Steam with it too. In the hopes a Dev spots one of our tickets I just want to add we've spotted an odd quirk to this bug. If you open the Steam Overlay while in game, your ping drops to a more normal level. The reason for this is a mystery to me but maybe it'll help track down the source of the issue. When you close the overlay ping goes way back up again.
https://community.focus-entmt.com/focus-entertainment/space-marine-2/bugs/229-high-ping-single-player-impossible?page=1
My internet is fine. Ruining the game for me as everything is lagging real bad. Audio is out of sync, enemies telpeort 20ft at a time so cant track them properly, cant see ranged attacks or block/parry alerts ect. i have tried offline and online mode and it happens in both scenarios. i have ran multiple benchmarks on pc and watched on task manager while running the game and everything shows fine. as it happens these silly little red bars appear on both offline and online mode and thats when the trouble starts.