The one after.
And you can ALWAYS run heroics and get upgrades, so 'nothing worthwhile' is silly, they're not significantly less likely to drop usable loot than mythics at this point due to the ilevel cap being so low. Similarly, world quests repopulate multiple times a day. pvp ones like every 4 hours, those give tons of ap. Speaking of, spamming dungeons is the fastest AP by a mile. Heroics are awesome.
I'm almost 22 thanks to dungeon spamming heroics with a guild group/840+ pugs. Works like a charm...
Still not seen a single legendary, though!