I had massive problems with that battle my first go-round with him as an Electrical mage. I couldn't get to the clear areas between the red circles in time. I was a bit impatient so I decided to approach it with a different style of build as I was already facetanking everything cause of my play-style, so I opted to make a new character that was sword & shield based. I did nothing but nodes I thought would benefit my survivability and viola, I beat him the first time. If you're too squishy and not patient you will just die over and over, I'm sure you can beat him given enough time and item drops, but I opted for a character around my actual play-style.
I know this doesn't really help your current situation, but all I can say is, I did have a little bit more luck as a mage when I would just sit right next to his shield.
I did however learn while playing my facetank guy that you can stun him when he goes into that phase. So when he stops attacking, jumps back into the center and does the shield animation, I would jump and stun him and the animation would go away and viola no more instant death circles from hell. Now it's just a grind till you max out gear and builds!