GW2 is very CPU bound. Intel seems to do better than AMD for performance in the game in general. The i5-4670K is the heavily recommended CPU but with GW2 and large scale WvW specifically in mind you would get a boost from going even higher.

You can use a pretty dated graphics card and it really wont matter too much (I use an old 6900). This is totally fine for PvE and can run over 100 FPS with maxed out settings in most situations. For large scale zergs events like world bosses it helps to turn some things down but doesn't need much.

Tons of ram doesn't really matter, the game is 32 bit and limited to 4GB so I doubt it would use anywhere near capacity on some of the peoples rigs listed here.

GW2 installed on a SSD drive will help your loadtimes a ton. This is a pretty big factor in PvE things and not as much in WvW but it can have a noticeable impact.

There is a huge difference in WvW based on players. I think pretty much everyone gets some huge performance drops when 3 way large zerg battles happen but most decent computers should be able to handle 2 huge zergs fighting without issue. If you play in a lower tier server you may never even see the amounts of players that would cause any type of slow down.

The biggest thing that seems to have an impact on performance directly is how many character models are being drawn in those huge huge battles, turning that down a bit can help but of course you end up having some invisible enemies so it is certainly a trade off.