I tested soloing heroic area on Ilum and I managed to kill them without death and it isn't hard, but it isn't easy as pre-4.0 and i noticed that credits are nerf - I used to earn a lot of credits in pre-4.0 but not anymore, probably 1,000 less at worst. It take more time as well - it used to killing them very fast in pre-4.0.
I noticed that companion's gears aren't matter anymore because 4.0 take stats out.
I recommended you to use companion as healer and you have to do fast - DPS > heal > DPS > repeat. Just find companion that has high stats than other companion. In pre-4.0, I'm unable to soloing heroic area on Yavin 4 and died instantly but I'm not sure about current patch - need to be tested, also I believe that I use wrong companion or rotation at first time.
I have mixed feeling about level sync and I do believe that they need be toggle on and off, but credits earn from heroic area isn't generous as pre-4.0.