May I suggest a "Roll Down Dates in Gantt Chart" with a checkbox "include milestones".
It would be similar to the Roll Up Dates feature but here subtask would shift if the parent tasks is shifted (even if no dependencies have been established).
Why this feature if you can work with dependencies? Because:
- often it is not convenient to work with dependencies
- if you are new to Wrike it makes working with Wrike a lot more easier (people just expect Wrike to move all containing sub-tasks if you move a parent task; it's the one basic feauture why people are turning to a planning tool in the first place)
- it would make life even more beautiful for Wrike users then it is now.