I dont know if you've played Makeb yet, but the sheer number of mobs means the stealth classes have an advantage over any other class---you can always force cloak your way out of any situation if you happen to drag multiple mobs by accident (which would mean instant death in a lot of cases, even using your Heroics).
As for the normal worlds, it kind of bothers me having to fight my way through long dungeons to get back out after I've exited the story area at the end--often, the credits and/or tradable loot just isnt worth it IMO. Like House Rist for example. I loved how I could just stealth my way past the respawned enemies rather than waste a good 15 minutes grinding my way back out again.
Also, another benefit----as some of you know, there is a small Level 55 grouping on a hill on Hoth, which, if you stumble upon as a level 35-40 (i forget what level Hoth is for either side), you would have zero chance of surviving, but as I did with my stealth character---grabbed the loot from behind the level 55 Elite guarding it, then force cloaked my way out of there. I dont *think* there is any way to do that with another class besides stealth. Maybe somebody has a reasonably strong tank companion at 35-40 that could survive the beating long enough for you to loot and run (if you somehow managed to dodge the level 55 angry tauntauns that line the sides of the level 55 mountain, LOL) but then you would be paying a good part of that loot back to repair his/her armor as they would certainly perish quickly.