Can I see an overview of my settlers?

No, unfortunately there is no overview of what all of your settlers are doing. However you can see what each individual is assigned to if you have visibility of that individual and their assigned task - this picture will show you what I mean:

This settler is only assigned to half of these carrots, another settler is doing the others, so when I target this settler is highlights half of the carrots.

There is, however, an overview of all of your settlements available in your Pip Boy, under the Data > Workshops tab:

This will warn you of any issues at each of your settlements.

As of 11/11/2015 there is no settler interface.

The beta patch for 1.3 released on Jan 15th does show settler assignments when you hover over the settler. A wonderful and much needed improvement.