While working on the quest line for the Legion Enhancement Shaman artifact quest, my character Wayama-Whisperwind fell into a hole in Deepholm and was unable to get out, since she is too low level to fly (level 13). The only way to get unstuck was to hearth.
She dropped her Enhancement Shaman artifact quests in Deepholm, and was unable to reacquire them in her class hall.
She went to Orgrimmar, and the portal to Deepholm is unavailable.
In pre-squish Legion, it would have been possible to return to Deepholm because she would have opened it normally, and would have been higher level to access it. Because of the level squish and the way Cataclysm zones work, at level 13 she is unable to access Deepholm and get back into her quest line.
Shaman on the Enhancement Shaman quest line need a way to return to Deepholm if they have to leave the zone for one reason or another (in my case, because it was the only way to get out of a hole too deep to walk out).