With the Warband and my experiments with https://github.com/Ioney/QuestTracker/ i see a lot of hidden tracking quests being completed right at the login of a new character.
Some of which we don't know yet.

I think we should be tracking completed quests , mapid&timestamp independently of the zone being "marked" for tracking.

Treasures, Rares, hidden tracking, happens all over azeroth now, even in the classic zones, cities, dungeons and so on.
It also should happen right with entering world that we ask for completed quests and add everything we don't know.

This could be a good idea. However, note that it is already a little painful looting in zones where quest completion is tracked. I wonder if that can be optimized a bit to make the whole process smoother.

In addition to that we could make things more robust by also having a fallback like Ioney/QuestTracker@e4c28b3 so we are sure that the quest data is as complete as possible as this isn't relying on the quest being in the log. This can also track name changes for already completed quests and print them