Question about Coldain Ring #9Follow

Hi all, i need some help from someone who has already done the 9th coldain ring.

I was able to get all the way past Peffin, and decided to go try Doldigun in Kael (in the Iceshard keep area). Since i had been able to solo the first few nameds i thought it would be easy.

I was wrong, I turned in for the ring (to turn in to Juliah in Icewell to get last head for the quest) and proceeded to attack. I was doing fine until i got to the last named giant who was resistant to all my spells, i got him to 18 before he ran into a bunch of Giants and i had to gate.

My question is, do i have to start from the begining agian? Since i already have the ring, and its possible to do the event without the note (for plate armour) is it possible to just redo the event and still get the head?