Same for me. I also got this from the Mages Guild - the first quest where you just get a bit of money for signing up with the guild - on a character who already completed all of the guild story line.

For both the werewolf encounter and guild initiation I was in a region that didn't belong to my characters' home alliance.

EDIT:
I just found this in the One Tamriel Patch Notes:

Hircine's Gift: Player characters bitten by other werewolves can once again properly see Thoreki to begin the quest. We also fixed an issue where acquiring the quest from the scroll at the werewolf site would not let you use the entry portal.

Could it be that the WW-quest problem is related to this and players being infected by other players?

When you get bitten by a vampire or werewolf ingame, you get another passive (with the disease), than when you are a full vampire or werewolf. However, for all vampires (regardless of who bit them) and werewolves bitten by NPC werewolves, the disease passive is removed, as soon as you complete the quest. For werewolves infected by other players, the disease passive is never removed. I guess, this triggers Thoreki's quest. And the werewolf with whom I encountered this, was definately bitten by another player.