No, wrong. The departure lounges are all airside. In transit you simply need to go through a security checkpoint to get from the arrivals level to the departure level. You don't need to go through Immigration; the Arrival is landside, but not in the same league as the Wing or Pier. It rarely takes more than a few minutes to get through security, particularly if you you are at one of the more remote security points. The best one if you have your onward boarding pass (which I believe you will) is the one somewhere around gate 30, which never ever has a queue.