As of this update, all alerts are considered role-optional, which means the longer a group waits in the group-finder for a certain role (such as a tank or a healer), the less picky the group-finder will be about filling that role. For instance, if a healer can't be found after a substantial period of time, the role will be filled by another available role. This is possible thanks to the team buff. Any time three or more group members are within range and line-of-sight of one another, the whole group will gain a buff to compensate for missing roles. For instance, a group missing a tank will get a damage mitigation buff, a group without a healer will get a health regeneration buff, and so forth. The official post notes that "the buffs are by no means a replacement for having the actual role in your group. But with some self-reliance, it will... allow you to complete the Alert successfully." For the full details on the new system, plus other features such as Novice Raids, click on through the link below to the official site.