Are there any mentions in the lore as to when was the Ravenholdt (faction) founded? I can’t seem to find anything on the matter, except maybe the fact that they are also referred to as the Assassin’s League, but that does not contribute to my question at all.
I haven’t read any or are a specialist on this subject - I have only based on your question made a little Google search myself, so maybe someone have a more fulfilling answer than the one I will bring
According to this page, the user thinks the order was founded around The Second War, based on the architecture he sees in the old Ravenholdt Mansion.
It could be supported by this fan page, where she/she explains about the speculations made of what he/she have read:
When the King of Alterac betrayed the Alliance to the Horde, he and those nobles who had supported him were banished by Uther. When the Horde refused to offer them sanctuary they began to prey upon the very people they had once ruled over. Ravenholdt (I believe) came into existence to counter this threat.
And a little timeline
Wow, just what I was looking for, thank you!