Really? How many solid RJT teams do you have? It should only take about 15 "reasonable" squads to kill p1. This is also something that can be practiced in T6. The only difference is that Nihilus hits a lot harder in heroic, he's tougher, and he has a 50% chance to take a 3rd action (which is significantly less impactful post-nerf).
Good players should be scoring 8-10M in T6. The next time you try Heroic, make sure people don't post "crap" scores like 1-2M. Set a percentage threshold (based on the # of RJT squads you have), and don't let people post their scores if they're below it.
For example, if you have 25 RJT squads, set a limit of 5%. That way 20 squads who complete 5% can kill the phase. A couple squads might make mistakes and hit below that, but some of the squads should also hit above that, and in the end you should finish the phase. Then, focus your attention on the players who aren't following instructions - because early HSith attempts require a lot of discipline and organization, and players who don't follow instruction are usually just dead weight. Expect everyone to contribute - otherwise (IMO) they are indicating that they don't want to be part of a Heroic Sith guild.