I'm currently leveling my rogue alt after neglecting it for quite some time in favor of my main and favorite twink. Have been doing loads of Alterac and I'm honestly considering throwing both vanish and stealth out of my taskbar because I might aswell not have or use them. I can't count how often both players and pets have ignored vanish or seem to be able to see me from max range already.
One example was an warlock of equal level. After retapping a tower I fled from the crime scene because there were afterall three Alliance one of them being a healer. The warlock managed to get his imps out and those immediatly went for me, I vanished after using cloak to get rid of the imps and they simply didn't care attacking my anyway and forcing my out of stealth. Even another attempt did not solve this as they ignored vanish the second time just the same.
Another one was an warrior who was on a lower level then me. He was riding in the opposite direction of where I was heading, suddenly turned left to where I was sneaking down the road and charged me from max range.
The probably funniest thing was an hunter who didn't even stop attacking me, he didn't even lost me out of his target nor did I lose his pet and it's also nice that apparently one can be hit by traps regardless of cloak of shadows.