effort and allocation-based timelines?

We have a small team, with each member having very a specific area of expertise. As such, our timelines are defined by prioritization of tasks, dependencies, effort, and resource allocation.

I want to enter my tasks, set their dependencies, effort in hours, priorities, plug in the resources and set their allocation, and have the timeline built for me. 

Apart from MS Office, I can't seem to find a tool to do this. Everything seems to expect you to enter the completion dates for each task and just plug in the resources to hit the dates. It leaves a lot of unnecessary work on you to figure this stuff out, to hit dates that may just be arbitrary. That's all well and good if you have a surplus of skilled resources at your disposal, which I don't have.