Only one person needs to have done the access quest for the entire raid to enter.
Zone in and respawn areas are not necessarily safe.
Zone in Mystic lake and come close to the Sepulcher of Zan-fi then use the device you just get as reward with the quest The Rift to see the portal (Tanaan Portal Device)
If someone in your raid steps too far forward upon zone in (over the rocks as you come out of the water) you will aggro some trash mobs. Make sure your raid comes up out of the water to avoid accidently clicking and zoning out if this happens. The zone does have a lockout but some are more into the fight than into reading whether or not they want to exit a zone.