There are always those that love getting in large groups and doing scripted stuff that takes an hour or two and that is just fine, there should be plenty of that. But finishing quests that go on forever only to end up needing to do 4 man heroics is just plain stupid. You did all the rest of it alone, why screw it up and change it mid stream?.
Um, there is NOTHING like what you are describing in this game. All planet heroic missions are considered side quests and are therefore optional - they are NOT part of the overall planetary quest line. The only quest line I can think of that remotely fits into what you are describing is the "Jedi Prisoner" quests, but in all candor all that does is link three consecutive Flashpoints into a single story arc. And even it is optional (I did not complete it on my first character until I did the HM version of Maelstrom Prison at level 50).