To me the idea that stealth classes should be able to run up (unstealthed) to and simply trade blows with a non stealth class and expect to win is silly, the non stealth class should destroy the stealth class in a straight up broadside exchange. The balance comes from the fact the stealth class doesn't fight that way, he picks his fight he comes in puts the other guy in the hurt locker then wins because of his DPS lead from his burst. But if both the shadow and the sentinel have the same sustained DPS then what you have a situation were stealth is overpowering.
That'd be fine in GW2, in WoW and even in Warhammer Online.
In GW2 we have vast "outdoor" areas where a "rogue" can indeed do what you say on the unsuspecting passer bys.
In WoW there's much less outdoor but there's still some. Plus there's Alterac Valley with lots of sneaky places. At least this is when I played it.
In Warhammer the "rogues" intercept loners who move from warcamps to keeps or go to a capital city invasion. They can perch quite well in the most unsuspecting locations, i.e. in the middle of guards in a keep where people may even go AFK.
But in SWTOR? No way. There's no "outdoor equivalent" area with any score, points, gear or anything. You just gank level 25s on Tattoine, some on Hoth but that's like 2-3 guys up for ganking over a whole server of players.
So where do those "rogues" have to play? In relatively small areas and they must play nicely with location-constrained objectives. So in the end we have to gravitate around pylons, it's hard to catch unaware people in places they expect to be attacked.
TLDR: our model works in many MMOs but in SWTOR there's just no use-case for us.
In WoW and other games, "rogues" have a PvE and sometimes PvP spec made on huge sustained damage losing the CCs, but not in SWTOR.
So we are a fairly well designed fish... out of his water.