Do you have battle effects for Party Members set to limited display or none? You can't change how others perceive your effects, you can only change how you perceive others'. Which is the problem with the DRK aura, with my effects set to None for non-party members I still get this giant red glow around all these 'Look how unique/what a tool I am!' Dark Knights afk'ing around everywhere. With those same settings however for turrets I don't see effects beyond the turret itself, the first time I saw one placed somewhere in town I thought it was simply a minion since I don't see display names on most other players or their objects without selecting them.