Stealth doesn't work properly

I have had this problem from day 1. I’m a rogue and put 3 points in Master of Deception meaning in stealth “it is more difficult to detect me as if I’m 3 levels higher.” This SHOULD make it virtually impossible for anything my level to detect me unless very close to them.

However, all game everything–beasts, humans, etc. that are my level detect me upwards of 10 yards away. I know some things detect stealth easier but this is EVERYTHING. I literally can very rarely get close enough to ambush or sap anything that is my level, even a level lower most of the time. It’s supposed to be as if I’m 3 levels higher. It actually plays as if I’m 3 levels lower…

BTW, have played a rogue ever since 2004 and every expansion since…never seen anything even close to this, stealth has always worked the way it should. Something is clearly wrong.