Most heroics don't have prerequisites to do. And all are repeatable daily, that's why the mention of them being good credits and xp. Plus the fact that they're repeatable does help for helping out others, unlike WoW where it was "you did it once, never again, good luck people who are starting the game late and there's no one around to do the group quests with".
"Sir,we are beginning our search for these rumored 'underwater villages'.They will not stay hidden for long". -Battle Droid Commander OOM-9!