I thought it was kind of expected that Pikachu lose since Doryuzu had a type advantage (both resisting Pikachu's Iron Tail and not being affected by his Electric-type attacks). Not to mention Pikachu has a weakness to Ground. However I think it was very realistic how they showed Pikachu could still hang in there for a long time. It was a good battle and I wonder if Iris will ever use the Wings that she won. Her Doryuzu also had a lot of experience before, which just goes to show how strong Pikachu is.
This was a pretty cool battle and a nice end to the Don Battles episodes.