I would say that they are really good because of their kit that features elemental resonances for the team to enhance your overall damage potential. Nemesis focuses on Volt, Frigg on Frost, and Claudia on physical, which can turn out to be a decent character investment in the future. What I mean to say is that it may look like 15 % resonance isn't much, but when your characters' damage starts to scale in thousands or even millions, if you are heavily invested, then these percentages can make a day and night difference in damage output.