[SsSam]

Yes, my Theurgs will cast spells as slaves.
They will also cast scripted spells as slaves.
They (both Theurgs and Theurg Communicants) will use the bows when they are not in a communion.
In a communion as slaves I can't get them to use the bows. They do appear above the masters in the army setup screen.

It does seem like a large thing to be altered without being mentioned in a change log. ....