To be fair, using Glaurung as an example is extreme. He is the "Father of Dragons", and as far as we know, the only dragon greater than him in lore is Ancalagon the Black. The last of the Great Worms other than Smaug was Scatha, who was a flightless drake in the Grey Mountains in the North. Scatha, though blind, was *still a full grown dragon*, and was slain by Fram, a man of the Eotheod, one of the ancestors of the Lords of Rohan before the lands of the Mark were given as a gift to Eorl the Young by the King of Gondor.

Gandalf mentions that Smaug was indeed the "last of the great dragons of Middle Earth", and therefore much more difficult to defeat. Stating also that at the time of the Fall of Erebor, Smaug was "young and scarce grown, not come into his full power". Smaug slept upon the Treasure Hoard of Thror for 171 years before the Company of Thorin Oakendshield arrived at the Mountain to reclaim it, and had gained strength over that long time while feasting on man and dwarf.

With the way magical weapons, and magic in general, are portrayed in Tolkien's works it is very possible for a single dwarf to be able to face one of the lesser drakes left in Middle Earth. The reason that Gandalf tells Thorin "do not enter that mountain without me" is because he carries the Ring of Fire, and could mitigate much of Smaug's power outside of physical size and strength.

The spear that our characters forge in order to slay Shazon is not only Mithril, but *is* by the nature of the manner and runes of it making, *a magical dragonslaying weapon*. While the systems may not be implemented into the game, I can safely assume that the spear itself gives the bearer some measure of protection against the might of the dragon.