I would go for something like Knight's Challenge or a straight up damage reduction tanking cooldown. I do not know how balanced that would be, but with block severely lacking in my opinion, a straight up damage reduction cooldown does not sound like a bad idea in my book and perhaps it could be something like 20% for 5…
I just did this fight about an hour ago on a 26 GF and I had a blast. The challenge was just fine for a GF. I had the cleric companion and she got hit twice and only lost about 10 percent health (judging from the green bar under the portrait). I never used a pot either. Unrelated note: the music during the fight was rather…