I use your Plugin via shortcode to list all authors of my site. I'm not sure why, but the filter by
role="Author" did not work, until I removed the
blog_id from the query args. I do not understand the relation between those arguments (still a beginner in WP yet), but wanted to let you know.
Furthermore there are some notices about an undefined var '$list_id'. I added it to the globals to get rid of it. Did not use the filters anyway.
Thank you for your great plugin,
I like the simple customizable function.