It would be GREAT if you could allow a preview of the card instead of having to add it to your class. By not allowing us to preview, it really slows down the research. Personally, I would probably stay away from Commons if I'm not allowed to preview the card.
Now that teachers can Preview Draft Assessments there is a way to preview assessments without making them available to students.
Import assessment from commons as a Draft
View as Student from teacher account
Preview the assessment
Make active if everything looks good
Delete if you don't want to use it