Malyck
I see no need for a retcon. He’s from another Pale Tree somewhere to the west. After you do that part of the PS he goes off to find this tree for himself. Probably a plot thread left open for a future expansion.
I see no need for retcon, and I don’t see why he’s the “single most important” element either. Please explain why you believe this, otherwise there’s not much more to discuss.
Stop treating GW2 as a single story. Each Season and expansion should be their own story.
Why would a retcon be needed?
ANet have a lot of background here, it makes sense that we don’t understand everything yet. There’s a great deal of mystery in the game, and it’s not a mistake.
I see no reason for a retcon. Trees grow from seeds. Seeds come from trees. Something needed to grow the seed that the Pale Tree come from. Why can’t another Pale Tree exist? We have hints that some might already exist in Cantha and Elona already, if I remember my GW1 lore correctly.