I suppose it's up to your personal style of play. I can tell you I got her today and spent all evening maxing out her stats as much as I could (all upgrades, 10 Heroic Challenges) and I went with the Spectral Lightning upgrades. She was laying waste to everything with very little effort by the time I was done.
Yeah. The Heroic Challenges are easy with her. I just finished all of them and had very little trouble. I think she is seriously one powerful character.