The grail addon show only eastern kingdoms and Catacylsm and kalimdor hero's call quest when completed. The addon don't show outland, northrend, and Pandaria hero call: quest when completed except for Hero call: outland, Terokkar Forest, Borean Tundra, It will be nice to see all the hero's call quest in the list.

Which faction are we talking about?
Do you have examples of working and not working quest ids?
Usually we rely on the game marking the quest as complete.