I think Drae is right; above level 50, the level-50 phase of Arathi should be available for you. I think.
Just fly there and see if the mobs are level 30 or level 50.
If they are level 30, look for a speech bubble on your map, centre of the south of the zone, by the river inlet. That’ll be Zidormi, whom you can speak to to set the phase.
If not, if you have to open the phase/warfrront, let us know and we can look up Wowhead - 'cos we’ve all forgotten 