I propose that Jujus and Deimaginators not be able to "see" you whilst stationary under the ff conditions:
1. Newly entered map (via logon or map switching)
2. NPC is off screen (as opposed to suddenly stopping right beside them and expect them not to have seen you doing so) and you remain still for 3 seconds (20 game seconds)
I couldn't think of a way to compensate for those lagging and couldn't be transferred on to the next map fast enough, but (2) seemed an okay compromise.