The first time, they could have likely beaten her after the rain stopped (Haley was planning to do so.) The only reason they didn't was because Roy wanted to bone her and Durkon mistakenly believed the storm had been a sign from Thor.
And even the second time (which the description does make out to be a lot closer than you're saying), the fact that Durkon refused to contribute and only healed people slightly to stabilize them was a huge factor. If he'd been attacking or providing proper support, Miko would have lost easily. And, again, the misconception that led him to that position was pure luck.