We (3 dudes) use LAN to play, with VPN being created via ZeroTier (p2p essentially). Originally tried Hamachi, ping instantly went 10 secs or so.
The base ping is around 150±50 (which is already much higher then I would expect). During the campaign it behaves wildly, often jumping to 400-800 (sometimes even up to seconds).
I am reasonably confident in our ISPs capabilities (I have fiber with up to 100Mbps down\upload, they have similar), and games like DOTA 2 or LoL are displaying very consistent behavior in this regard (~50 ms ping without jitter). I use WiFi but the area is semi-rural with 2-3 very weak WiFi networks elsewhere, so no radio overlap should influence anything. They use Ethernet.
We all live in the same country, and they live in the same city. Problem is persistent regardless of who hosts and who joins (we tried all options).
Any advice, please?
I guess it might be worth adding that I have optical modem + router (27016 port forwarding enabled in latter). The other 2 have just 1 router but they also experience the same problem.