My PC is a few years old and due for an upgrade, but it still plays pretty well once some of the settings are turned down. I don't even notice the medium settings once I get into playing the game. I'm running a mix of high/medium/low with some effects disabled.
I did have one WvW battle where I just got into the WvW area and was trying to run to the battlefront with speed buffs. I saw a crowd of my own team running the opposite direction, but I didn't see what they were running from, so I kept going forward since the battle lines looked further ahead. All of a sudden, I started taking damage and ended up dead although there was nothing around me. After a few seconds on the ground, enemy players started appearing all around me in front and behind. So, a huge mass of enemy players was all over me, but I couldn't see them at all for a while (much too late to avoid dying).
That only happened once though and it was just after I had gotten into the WvW area, so maybe that was part of it. Anyway, lesson learned.