As a rogue there are 2 different buffs you can get from coming unstealthed
Assasination - Overkill (Reduces the energy cost of all skills by 10 for 6 seconds)
Sub - Master of Subtlety (Increases damage done by 10% for 6 seconds)
Okay, now onto how you bug them to stay PERMANENT!
I discovered this by accident and haven't tested everything out yet.
What you need is a druid friend to cast Cyclone on you
Cyclone is a 1.5 second cast with no haste. Pretty much with about .3 seconds left on the cast, stealth, when you stealth the cyclone will still go through, but you'll have stealthed and have gained one of the two buffs. But for some reason, the buffs don't have a timer, at first I just thought the Icon bugged, then tested to see if there was a damage difference between when I had MoS or not. There was.
Then I decided to see if it worked for Overkill, it does.
Note I haven't tested it all completely and plan too.
[ame="http://www.youtube.com/watch?v=gSQ7Xy7sTq8"]http://www.youtube.com/watch?v=gSQ7Xy7sTq8[/ame]