There is a requirement that seems to be missing in Aha!.
You can create visual dependencies on the Releases Portfolio view (Gantt chart) in the following ways:
Release phases and milestones (goals) can be linked to release phases and/or milestones of the same or other releases across products and product lines.
Features can be linked to other features in the same or other releases across products and product lines.
In both cases, a phase or a feature has a due-date by virtual of being on the Releases Portfolio view (select features can be added to the view so not all features must have a due-date). If any of the phases/milestones/features are pushed out their dependencies will also be pushed out so that they cannot start until those items they are dependent upon are completed.
For more see these two support notes: