I've leveled up an Operative and I've never seen this 'super-stealth-detection' people are claiming all droids have.
1. Bosses have insane stealth detection, and you can tell because the stealthed person will get a symbol over their head telling them they're about to be detected. A few seconds later the boss usually aggros.
2. Some (note: SOME) droids have a stealth scan ability (note: ABILITY they can activate, not a passive trait) that looks exactly like the BH's stealth scan. Yes if you stealth anywhere near that thing you will be knocked out of stealth immediately, but it's a clearly visible animation that is easily avoided.
If you stealth up to a non-boss droid that does not have a stealth-scan ability (or has just used it and the effect has faded), their stealth detection chance is the same as any other mob.
ALL droids don't, though many elites (esp in flashpoints) do have the same passive stealth detection as bosses.
The pack mentioned by the OP in Hammer Station has a pair of gold star droids that WILL spot a player in stealth long before they get in proximity agro range, WILL engage the group in combat if the player in stealth does not immediately drop stealth, and WILL switch agro to a healer if they happen to be casting heals.
While it isn't clear exactly what happened, listening to the OP go on and on about how much they know about stealth while clearly demonstrating they did NOT notice the pair of droids in that particular pull having the passive stealth detection / auto agro ability leads me to believe the group kicked the OP for pulling.