When assigning a task to multiple people make it so that the task has to be completed by each individual assignee.
Currently if one of the multiple assignees completes the task, the entire task is completed and no longer shows as a task for the others. This defeats the purpose of this app. Creating a separate task, which is the same task, and assigning to each team member is very wasteful, painful, and will prevent your users from using your product. It's unacceptable.