As of patch 6.1 addons cannot find a rare without you mousing over the rare. Whilst this is fine in most cases, the more desirable rares have a lot more competition to tag & bag.
What you need:
NPC_Scan from curse: _NPCScan - Achievements - World of Warcraft Addons - Curse
_NPCScan.Overlay: _NPCScan.Overlay - Map & Minimap - World of Warcraft Addons - Curse
Turn on all nameplates: default is Ctrl+V
What this does is make friendly nameplates show to make it significantly easier to see a rare. In particular items such as camel statue as for instance the overlay shows you spawn locations, plates will help you see the name and then to confirm it's the rare NPCScan will go off upon mouse over. If you don't see the nameplate simply fly/go to another spawn location.
Simple but effective and I hope it makes your rare hunting a bit easier.