Is it worth starting over?

I'm level 13 and have hit a wall in prophecies. I've read that it was designed for parties of real players, the missions I'm doing I'm getting rocked. I run into groups of healers and can't out damage the healing then my team slowly dies. It's not very fun right now, I was thinking of doing nightfall to get hero mercs, is there some other way I can get there and start that expansion then come back later? I believe I'm at the frost wall right now.

Edit: I was able to get the mission completed. I flagged mercs and pulled packs with a bow, the separating of the mobs allowed me to burst some down and remove some of their healing. After that I noticed the dwarf died pretty fast, so I cleared the path first then went and grabbed him to work the ballista. Thanks for your help people.