Just opened a 5* and got Emma Frost suggestions please

How is emma frost ? For which content is she suitable i saw her in god tier (A) in seatin list she doesn’t seem to be useful other than Aw defence . i became a cavalier a week ago so i am planning to do variant and explore act 5.
suggestions would be great

P.S Is she worth ranking up to r4 unduped
and how to use her to her fullest potential