Alrighty guys, i have been the victim of this bug for a few days now, and it is a real one. There is a bug which allows you to target stealthed players from any distance in arena, it apparently is an ingame mechanic and is proven by this thread.
WoW Forums -> Seeing stealthed from anywhere on the map.
I am putting this out to there help but also to figure out how to use this myself.... always finding the resto druid would make me win every game. Hope somebody out there is willing to share
Dave