is there a way to get to the Domain of Istan other then by the Astralarium Waypoint (i mean once the area is unlocked?) Is there a series of portals or anything? or is it just that waypoint?

There is a ship in Amnoon that will take a character whose already unlocked that map. For characters that haven't been there yet, you can buy an Istan Portal Scroll (at the docks in the Domain of Istan).