This is all my opinion.
Piranha Strike - While it's a good feat, I just feel there's other, better feats you'll want to pick up instead. It also suffers from having a 3/4 BAB, which is not good since you need to land hits to get your SA in.
Throwing/Ranged attacks - These are all feat intensive builds. You pretty much have to base your whole build around them and they usually don't come online till the higher levels.
If you do decide to try building something like this, it's suggested to use a Ranger or Slayer type build. There are some ways besides going the Ranger/Slayer but involves using a bunch of different archetypes.
Picking up a level or two of Barbarian - Don't think it's worth it. It's a balance act which you have to ask this question. "Are you getting more then what you'd be giving up going 'pure' class?"
Half-Orc with Bite - ...nah, while the bite can be fun story wise, nothing says rogue like a halfing. Other problem is you're going to be missing that bite attack, a lot, specially when you tack on the TWF -2 onto that -5 for the attack roll.
Playing the Half-Orc Slayer - From what you've mentioned about your other 2 players this sounds like the best option to me. Rogues can be a lot of fun but they require teamwork with your fellow adventures, mainly as flanking buddies. Being a Brute Slayer doesn't require this as much and actually works better when facing monsters with DR.