Have you ever had requests to change workflow approvers when there are 10 items pending approvals. If yes, i can show you how to create a workflow without having to change the workflow where the task is located. In this scenario you will use two workflow. Two is always better than one in case of nintex if one is too big.
OK, here we go.
This is it. Now you have a dynamic approvers workflow for which you do not have to modify the task workflow or have to wait for task workflow to complete. You can always go and change the first workflow to change approvers.
Note: Make sure you are not passing the group name or else it will not work (it did not in my case). We are doing this to avoid SharePoint groups also.