With the dueling feature i can confirm that PVP causes lag. Not the crowd or casting abilities it happens when we attack other players its not our hardware or connection its server side.
@ZOS you need to upgrade your servers or change the data transfer way between server and the client. My latency was 200 in deshaan and it still at 200s non pvp areas but i went to deshaan and people were dueling and my latency increased 150-200 more not my FPS but the latency.