Sounds like you're being too passive. Eat a lox meat pie, bread, and fish wraps, and fire resist potion. This will give you plenty of health and enough stamina to fight.

When the boss does his big fire aoe, just tank it. The fire damage will be greatly reduced, so you can keep swinging away. If your health is starting to get low, drink a medium healing potion. When the boss calls in meteors, hide behind one of the large stone pillars and just regenerate stamina. Repeat until killed. Takes like 4 minutes.