Yagorath is mainly point tank that can't atack enough in mobile form. As long as you play on Exterminate and have at least one beam she is no danger. You can counter her better if you also have cards that shorten cooldown of your Beam.
Check the ability. If its exermination, go in mobile form when ever shes closeby, Furia will usually try to hit you with the solar beam the same time you change forms so you can avoid it in time. bait it out.