I dislike how they are dispersed, in area, level and zone. So you can spend 15-30 minutes, looking for a group, complete this quest, continue questing, and you are right back looking for a heroic in a different area. There's no flow.
In my opinion, this should have been done differently.
All main planet and class quests should be solo-able. After you complete planet quest line, the Bonus series is now unlocked, and has 3-4 Heroic group quests you can adventure on.
Currently, do section 1, wait for heroic, do section 2, get group for heroic, etc... complete planet series. Go back and do bonus series.