I actually stayed in front of the dragon, waiting for him to cause some damage,
then smacking him a couple of times, hoping my levels would reap the 'added experience bonus' someone mentioned earlier.
Poor little dragon eventually died.

(He must have been lonely anyway. He was all alone.

I even wasted a coin, taking the grand tour through the room by the firestaff gem, where the final resurrection alcove resides.
(I always wondered why that door closed after leaving the close proximity.

I chose to leave the firestaff for later (first time). I haven't even visited the spider rejuvenation area.
P.S. It was a pleasant feeling, the first time the dragon wasted a fireball over my left shoulder.
(There are some advantages to having a smaller team of heroes.)
I was surprised to find out how easy it was to get through the game with one hero.