While the rogue still has the Vanish buff, Stealth is several levels higher than it is normally, allowing the rogue to remain undetected, even versus players that are much higher level.
It was like this back then, on Nostalrius I have been already charged while having the Vanish Buff active (by a Player 3 levels higher).
Both - Vanish stealth level and normal stealth level have not the right values.
It's hard to find any evidence since you won't find any videos of someone beeing charged while having the buff.
I've been playing Rogue since beta untill TBC and can only contribute with my knowledge from back then and it wasn't anything like this.
cheers