Actually, you can make it much easier on yourself if you return to the challenge from, say, level 10 or so, once you're more levelled up and have a better equipment. I tried to put up with it right from level 6 and it took me approx. 15 retries until I finally realised I really do not have a shred of chance of making it. Then I returned from level 9 (with Zhandul's Orb in hand) and then it only took me about 4 retries to nail it. Then again, I did only have ony fighter, one rogue and two mages, one of which was in the front. I believe it could be considerably easier with two fighters instead.