The most recent State of the Game article has been posted on the Guild Wars official site, and wraps up their look at midline strategies.
Previous articles in this series have discussed individual Ranger and Mesmer responsibilities in midline shutdown. However, in an actual GvG, with an eight person team, these professions rarely work alone. The midline of a good team works together, much like the frontline pair does. This article covers the communication needed for efficient midline synergy. Throughout a match, the midline's communication should focus mostly on targets, skill shutdown, and team status.
‘Targeting communication’ is identifying to your team which opposing player you're shutting down. Even though it is typically undesirable for you to camp on one target, calling out that target gives your teammates enough information to find another target to shut down. For example, if Diversion is a problem for your backline, you can have your Ranger temporarily reserve Distracting Shot to take care of it. And if your Mesmer is on that target, then he or she can swap targets while your Ranger takes care of any other skills the opposing Mesmer tries to use.
Read more here.