Demo: http://output.jsbin.com/vaviwa If the inputs/labels inside a fieldset (or role="group") are wrapped in divs - they will announce as "one of one" rather than "one of five" (if there are 5 inputs). The issue can be fixed by placing role="presentation" on the parent divs. If there are multiple levels of divs - only the immediate parent of the input needs the role.
<rdar://problem/26856152>
Looks like this was fixed in iOS 10!