Got the Tyrande’s Vengeance quest on my Alt. (Had already completed it on my main).
After the initial part in Stormwind, where you’re supposed to take the Portal to Zoram’s Strand. I do so, only to be met with an infinite loading screen.
Game becomes unresponsive, so I Alt+F4 and restart. Only for my character to spawn in to the Warfront version of Darkshore.
Happened multiple times. Still unable to take the portal and advance the quest.
Any update on this? I am currently experiencing the same issue. I take the portal to Darnassus (Supposed to go to Ashenvale I believe) and I am hit with an infinite loading screen.
Same here ! Just tried this quest today…
This is legit still happening and I can’t do this quest.
Still happening to me…
Happening to me too today on my 4th alt. Take the portal…end up on the shore on my own in the battleground rendition of Darkshore. Enemy territory. What is up with this??
Same here, happens on my main, can’t do the quest. 
I am having this issue as well. I am running no addons when attempting to take the portal at Stormwind harbor.
EDIT: The reason the loading screen is hanging is because the quest requires the original Darkshore. After you are forced to restart WoW, speak to Zidormi to phase to original Darkshore. From there, return to Stormwind, take the portal at the docks, and you will teleport properly to Rut’theran Village. The quest markers will erroneously point you back to the Stormwind portal on the Rut’theran Village docks. Ignore that world marker and take the flight path to Blackfathom Camp in Ashenvale.
Here is the solution:
if u stuck on loading press ALT F4 to close the client. Then log in u shuld be on dark shore. Talk to Zidormi to get to the past and then open ur map u shuld see the quest marked there now. Take the flightpath south and talk to Velen on the ship 11 18.
Good luck!