This is less a bug and more a harmful design flaw.
When Backbiter throws you backwards you cannot attack (or take any actions) until you arrive at the destination. That sounds normal and reasonable, BUT, in this case it prevents and delays Orphea’s basic attack, which prevents and delays her Trait and thus oftentimes a critical heal. In some situations Backbiter just ends up being a deathtrap.
Without Backbiter you can Chomp and hit with Overflowing Chaos straight away, gaining the heal and attack instantly, which is also great synergy with the Lv13 Abyssal Symbiosis talent. But Backbiter makes you unable to gain any these benefits until after a delay which often results in missing out on the attack & heal completely, if not outright dying.
This is a talent that actively makes her trait worse. Please allow Orphea to use her basic attack during Backbiter.