I generally only do Heroics if grouped or if the mission is green. The bigger you get the less likely you will be able to solo Heroics. Most the time you are looking at 3-4 elites at one time, and you can only CC one, maybe two if a droid. You might be able to get 1.5-2 of the elites before the CCed ones wake, but you won't be in any shape energy or health wise to keep fighting. Really it's a major pain and time sink to solo Heroics.