Dals are difficult dogs for a few reasons -- extremely high energy (that doesn't really tone down that much with age), a high level of athleticism (energy+athleticism=naughtiness when you are away), emotional inconsistency (if they are calm the slightest thing, like a light suddenly shining outside or a bird flying close by, or heaven forbid a squirrel showing up will turn them into nuclear balls of loud aggressive energy with no time lapse between calm and chaos), they have very loud barks which they use with little provocation, and they shed heavily daily (women hate this!)
They have much on the good side of the ledger -- but those are the reasons people think of them as difficult.
Thanks for explaining the nature of Dals so thoroughly :) I've seen the squirrel thing in action with other dogs--my grandparents' St. Bernard used to act like that whenever he saw a squirrel, too :)