Selene is pretty reliable when the healing demand is incredibly low like in the 50/60 roulette when everyone is way over geared. I use her frequently just for fun but I have noticed that her Silence gets used with no actual effect pretty often. Im not sure if it's just late or being resisted but if she is on Sic in a boss fight you will see her try and fail to Silence all kinds of things and it's obvious she isn't busy casting Embrace if the Tank has full health. It's really weird.