Unit attack ranges should be shown for selected units or for the unit the mouse is over if nothing is selected. It's often desirable to see the attack range of what you have selected, which is often nearly impossible if you have a lot of units. The reason this is hard is you have to zoom out to see attack ranges, then it's often impossible to highlight the right unit amid a ton of close together icons to see their ranges.
Also the range (eg attack) is only shown as a thin red circle. This should be more obvious, such as a filled in red circle or at least make the line much thicker. It's really hard to see on some maps like Fields of Isis.