Packet loss.
You do know that Pingtest tests between you and the nearest server on Pingtest’s list right? Run it again and manually choose Dallas, TX as your target server, at least that’s closer to where the NA servers are located. My score went from an A to a B when I chose Dallas over the server Pingtest picked.
Also not every router in the chain between you and the target when using PingPlotter will respond. Many simply filter out ping requests or treat them as very low priority so those routers report packet loss. It’s not surprising that the game server itself is behind a firewall making pings to it unreachable.
RIP City of Heroes
As I mentioned in the other thread, please run Game Advisor and post the results. It does a tracert (trace route) to every A-net server node. Packet loss will show up clearly.
Get Game Advisor here:
https://help.ncsoft.com/app/answers/detail/a_id/7386/~/game-advisor-diagnostic-report