ISIS-705 (now fixed by Martin), where I wrote:
The issue here is that the returned Blob/Clob must be handled with a scheduled handler (see ActionResultResponseHandlingStrategy class) but it is also necessary to refresh the page by redirecting to a new page. (In the case of an action accepting parameters, want to remove the dialog. In the case of a bulk action, want to clear the toggles and refresh the list).
Haven't looked at how Martin fixed that ticket, but might be a relevant approach.