currently there is a increasing use of thieves in WvW. The tactics is usually the following: 3 thieves are in the (enemies) castle. We tried as a zerg to kill them, but you need approx. 20 min sometimes tro get 2 of them. The stealth disruption trap is almost useless now, since the death-eye is visible for approx. 2-3 sec now. They are almost permanent invisible anyway.
So if the zerg does not want to run for hours behind phantoms, the leader finally decides to ignore thieves. and go for fights then. 10 minutes later the castle is fallen. Half of the game mechanics renders obsolete, there is no point anymore in nurturing castles to higher levels, unless the full zerg remains in it.
that is no fun anymore.