The latest PvP State of the Game letter has been published at the official Guild Wars site. Focusing on rangers and their midline capabilities, here's some of Mark Yu's thoughts on the subject:
Rangers' roles are similar to those of Mesmers, but often broader in scale. As a Ranger, you typically have responsibilities to disrupt, pressure, and skirmish.
Disruption: using the skills on your bar to interrupt key opposing skills at appropriate times.
Pressure: applied through spamming conditions, as well as controlling position and movement.
Skirmish: providing solid split capabilities, both offensively and defensively.
Check out the rest of the article along with Yu's skill suggestions at the link above.