Some PvE locations are customized to varying extents - but as a general rule of thumb - if you find it on Google as an old school location of a mob, it should generally be there.
CapyBry and Allakazam (WaybackMachine'd!) and the like should usually be accurate. If you find something that seems egregiously off or missing - don't be shy about bug reporting it and we'll fix it up unless it was an intended custom tweak. The goal is to add a bit of "newness" to the world without confusing people expecting things to be where they always were.