If dps is too low i can assure you Selene will not necessarrely help you about that.
More S=tp burn faster and mana burn faster =bard must sing longer to recover that.Ofc it's you're wiping at like 1-2% selene will totaly help you.But if it's at 10% or + i don't think it'll help really.We solo tank this fight and Eos seems to be the best.