I don't see a problem with this mechanic because it allows your tank to establish aggro without you pulling from your huge burst damage. With my current gear I'm opening with like 5-6K crits on all boss mobs in EV atm. There have been moments where I've been able to get close enough to do my stealth opening as the tank pulls and I almost always pull aggro off the tank from the huge burst.
So even though I take much longer to get in combat I don't really lose any dps from the huge burst capability my class has. We also have talents which greatly increase our speed while stealthed which really helps getting into combat faster from running up from the back of the room.
This might not be a game-breaking problem for you, but for others it's game-breaking. There's simply no reason for a mob to be able to put a group into combat simply because their ability to detect stealth is longer than their aggro range. If their aggro range is a certain distance, their ability to detect stealth shouldn't exceed that range meaning if a mob is beyond the distance they would aggro to a character, they shouldn't be able to pull them out of stealth, either.