The typical known means to defend against Hide from Dragons are focused around dragons inside his lair, like using non-dragon minions, traps, magical alarms, dispelling screens and what-not, but that’s all only valid for a static environment.
How could he deal with this spell when going outside his lair alone to hunt? Specially if he knows there might be pesky adventurers trying to ambush him? And then do it efficiently (that is, wasting the least amount of resources, while hunting for extended periods of time)?.
I’d also like to see a solution (if possible) that allows him to retain his flavor, for example, he could (if the spell only cares about the type, unsure) trivially beat the spell by simply polymorphing into something non-dragon, but he doesn’t want to lower himself by transforming into a lesser creature, that kind of thinking.
For reference, Hide from Dragons, SC p.114:
Abjuration Level: Assassin 4, bard 5, sorcerer/ wizard 7 Components: S, M Casting Time: 1 standard action Range: Touch Targets: One creature touched/ 2 levels Duration: 10 minutes/level (D) Saving Throw: Will negates (harmless) Spell Resistance: Yes (harmless) Silently you make the motions and the dragon’s scale smolders in your hand. The rising smoke wraps around you and sinks into your skin. Dragons cannot see, hear, or smell the warded creatures, even with blindsense. They act as though the warded creatures are not there. Warded creatures could stand before the hungriest of red dragons and not be molested or even noticed. If a warded character touches or attacks a dragon or the dragon’s hoard, even with a spell, the spell ends for all recipients. Material Component: A dragon scale.