To be honest I never saw this as an exploit, an exploit is using a technique to gain advantage over other players, as other players could do it, and counter it - it is not an exploit. It was part of the game mechanic.
The people reading the patch notes clearly didn't realize the choice of the word exploit was that it got around the beam of light thing other war-zones used to denote primary objectives, that was the only problem hence it sat firmly in the bug category. It's just the fact that it was used in tandem with abilities players have that people suddenly call it an exploit because they see the flaw as a whole not as a sum of events.
At the end of the day the people QQing about this are either poor in team situations, don't realize they have abilities to counter this, or are spending far too much time farming kills and medals.
If you don't have any abilities to counter such abilities why are you even guarding the door, a marauder for example should be fighting the force of players that aren't stealthed, those with abilities to see stealth and can AOE should be guarding the doors, and the support players (healers etc) should be off to the sides supporting the combatants.
If you aren't getting this form of cooperation then join a guild and find people to group with because I can tell you now from the hundreds of PVP matches I personally have played, this level of teamwork does not happen unless your pug is comprised at least partly by a group of players who are working together.