Because in guild wars 2, the clipping issue is horrible in world vs world (WwW).
So you sometimes attack thinking there is only a group of ennemies while in fact it’s a full raid. And you only understand this when you are instantly killed wondering what has happened since nothing ever is displayed on your screen.
This problem is really killing WvW and will kill GW2 if it's not fixed.

Don't make the same mistake in Teso pls.