I would like to say that I notice lag like your describing with all players in the Ifrit fight regardless of region. The issue with player movement is simply that, while your character's position updates locally in real-time, the positions of PCs and NPCs update based on information from the server. This explains why it appears that other players move away from Eruption at the very last second. On their screens they are probably moving immediately. You can also observe other players and mobs moving through terrain when this happens and their local and server states get very out of sync. I think gathering and synthesizing are updated based on the server state similarly.

Oooh! I found a video which very clearly demonstrates this phenomenon, including synthesis. There was another one I was trying to find where a one player sits still while another runs around them in a near-perfect circle. On the stationary player's screen it appears that the moving player is moving in straight lines, corresponding with time when position data is received from the server.

Link to Video: http://www.youtube.com/watch?v=vb9BF50bPyA