I have done most on my main and some alts but that was mostly when current - I was wondering what folks feel are 'must do' legacy quests for a new boosted toon to go back and do? Talk Like a Dragon? lore & legend quests? some other language quests?
Learn all the languages, including Draconic. The L&L... if you are a low level toon, do all of them, they inform your Master Strike ability. But at end game, you no longer use Masterstrike much, so... If you are interested in Norrathian lore, do every book quest you can find.