Measuring progress thru the story

If asked "how far are you into the story and lore of [some expansion]", most players wouldn't be capable of giving a concise and succinct answer. Apart from not knowing how much more there might yet to be encountered (fair enough), they'd also not have a strong grasp on just what they have accomplished.

If asked "how far are you into getting to the level cap", most players would be able to give an exacting answer. Some would even be able to tell you their XP/hour rates and projected play times. All the numbers are there.

When I look at a few of the top MMOs, the reason why is pretty plain: the latter is measured in game, while the former is presented only ephemerally. Once you've completed various quests, they are wiped from your in-game quest log UI. There is no built in mechanism for remembering whether you've met various NPCs or not. A cursory exploration of a zone unlocks and reveals all of a map, and deeper and more thorough exploration is not rewarded beyond that.

There's an untapped opportunity to take a future game design in a new direction.