Subtask dates need to rollup into the parent task and automatically calculate the dates for the parent task. The fact that subtasks dates do not roll up into the parent task makes subtasks a complete waste of time. Every new user that I have seen create a project uses subtasks. We then have to go back and make them tasks in order to se them on the timeline.
We also need the ability to add durations in dates and have the dates automatically update based on the previous task or subtask. Without this ability it makes Asana extremely frustrating.