The mini-map already has a direction indicator (or location indicator if its in range) for any quest in the current region. The full map has location indicators for all quests in the current region as well as indicators at the region exit towards any quests in adjacent regions. Plus in most cases, the quest tracker and journal indicate where to go. I don't really think we need more screen clutter in order to tell us for a fifth time what's already shown in four places (two of which are always on-screen).