In DQK, though, if you let one dragon breathe, you are pretty much boned, because all the rest will follow in short order. When facing 20+ dragons at a time, you have to drop that number down fast before your party's turn ends, because if a few survive the second round would be... problematic. DBFs become the mainstay of my dragon-clearing by the time DQK comes along. Before that, I rely on Stinking Cloud. The dragonlance only is worth using in a few specific circumstances where you are facing just one undead type dragon that you can reach and attack in 1 round or magic-immune ones (e.g., Dave's challenge).
Some types of dragon breath are really dangerous. Green dragon breath is likely to hit the entire party and inflicts fairly high damage (but I think that its range is fairly limited). Blue dragon breath has a long range, it inflicts 80 points of damage to a target who fails his saving throw, and it can hit a character twice if a wall is nearby.
The other three aren't as deadly. Red dragon breath is fire (they also love to cast Fireball) and all your characters should be protected by Resist Fire most of the time. The breath attacks of white and black dragons aren't especially impressive in DQK. Besides, black dragons are more likely to cast Magic Missile than to use their breath weapon and white dragons are pretty rare in the game.
As for the less common types of dragons : the breath weapon of Death Dragons can inflict very high damage, while the breath weapon of Sea Dragons is about the same as green dragon breath (but the damages it inflicts are probably a bit higher).
I remember only two fights in which you have to fight more than 10 dragons : one happens when you leave the village of Bai'or in the south, the other one is the very last fight in the game. I agree that the DBF is the best way to deal with most of the dragons, but your wizards won't always be the first to act. Having two guys with dragonlances you can send after the most dangerous dragons (especially the blues) can really be a lifesaver.