Arbiter of Ash - impossible to travel between circles as warrior

When fighting the Arbiter of Ash, one of the attacks is circles appearing on the ground that you have to move inside before his attack, or instantly die.

Playing as warrior, even with +25% move speed on boots, for about half the circles it is impossible to move into them quickly enough to avoid dying. Even anticipating where the circle will be and moving directly towards it as soon as the previous attack is done, I am a long way off making it into the circle before I die.

I tried to beat the boss for more than an hour and was unable to get through this phase of his attack.

I was also unable to access my stash during the fight to try any different gear or skills to get past this. This was a very frustrating experience after spending weeks getting the fragments to access the fight.