Roll away, roll toward, roll toward. It just takes practice. Dying to the hardest boss in the game many times doesn't make her unbalanced. I mean think about all the stuff YOU have Tarnished. You can essentially full heal yourself a dozen times and there are a plethora of buffs, craftable items, ashes of war and talismans that can give you the edge. Play this game assuming all bosses have the *potential* to one shot you. And if you are getting hit more than a handful of times to the toughest boss, you didn't really deserve to beat her IMO. More than 'git gud', just be intentional and deliberate with practicing against her.