You can use the Subtask To Group Plugin to easily duplicate a task for a group of users.
It uses a regular sub-task as a template which is copied to the selected users.
- Any sub-task can be used as a template.
To create an exemplary template-task use "Create Template Sub-Task" in the "More" menu (more). - Adjust your template to your needs.
You can use placeholders in the template to access properties of the assigned users (more). - When your template is ready, use "Copy Subtask to Group" in the "More" menu.
Add the users or groups you need and proceed (more).