I really had no idea about Din's Fire with Dark Link. Heck, I didn't even know the Megaton Hammer was effective against him. What I did was just use simple sword skills to defeat him. I found it rather frustrating though, as it was a stalemate of sword strikes back in forth, until I finally hit him enough times to defeat him.
I thought he was a fun bus though. Personally, I thought the dungeon boss, Morpha, was the worst boss in the whole game. Just no... feeling to the boss, wasn't really scary looking, was so simple, and just nothing that was out of the ordinary. A better boss battle would have given me a better lasting impression, but I think Morpha fell a little short.