I have been running BC Heroics daily for transmog and whenever i use a flight path to go from point A to point B I usually fly over a rare spawn and my NPC Scan goes off. I remember the location, and as soon as i land i go and check it out to kill. They are never there, anywhere along their pat path. I Just assume someone killed them and move on. But recently i flew to Cosmowrench (the flight path just outside of TK) and my NPC scan went off for Nuramoc, i clicked on the portrait and he was alive and NOT SOMEONES PET. The best part (i thought) was he was located just outside of where i landed, so i instantly mount up and go to where i saw him. He isnt there, anywhere to be seen. So is this an issue with the Xrealm or what is going on?
What happens is that the rare you are seeing is on the server for the zone you started your flight from. For the whole duration of your flight you are still on the starting zone's server, but the moment you land you change to whatever server the x-realm thing wants to put you on, which generally isn't the same server unfortunately. I've seen this happen many times myself (seeing the huge infernal rare that is in SMV and going over to the area only to not see it at all).