500ms? No. 200-250, 300 at the outside for a US East Coast server. GW2 is more in the 200-250 range.
The lag you saw during the stress test is not representative of what to expect in normal circumstances. They were deliberately pushing the limits to see what the servers can cope with so they'd know where to set the limits.
Additionally they were having an issue with their own connection which caused heavy lag for a lot of people.
Not saying the tunnel couldn't help some people but it's usually pretty good, for a server halfway round the world...
"Wasabi is a sometimes food." - Elmo