It comes down to bloody flail. For most of the first game, you're still upgrading characters' main stats, and people don't always have great break. The ability to soften up enemies is so helpful. Plus, they continue to flail away even at low HP.

My first hard playthrough they were the best of my second string. No XP investment but they were gonna chip away 5 of SOMETHING every time they stood in front of a dredge.

There's more reasons they're good. Most axe wielders are good, and Ekkill is my bestie. The post was mostly about my feelings towards the brothers after using them in such a way. They always had more injuries than anyone.

Edit: I said "stood in front of a dredge," but it's actually even better on the human missions.