Story stuff like this is always synced. It always will be. This is the last dungeon of the baseline msq, people getting to it late should get to experience it the same way everyone else did. It's no fun to have this big cinematic experience (opinions may vary, but its still the lead up to the end of the story) and have to miss half the mechanics because the overgeared party kills everything in half the time.
Just deal with it until 7.1, then a new dungeon will be added that wont be item level synced, and Alexandria will be rotated out.