Social poll.

Just now, on the DF2 forum, they touched upon the following topic:
Creatures don't deal fixed damage, but rather fluctuating damage, often within a fairly wide range, depending on random chance. And in the worst-case scenario, it could happen that in a quick battle, your creatures will constantly deal maximum damage, while the neutrals deal minimum damage. Plus, there's also the triggering of abilities, morale, and luck.

So, I can somehow tolerate a one-sided, imbalanced quick battle if, in that scenario, your army performs at its absolute minimum potential, and the enemy's army performs at its absolute maximum. (However, it's completely unclear how to account for negative/positive morale, luck, and abilities without resorting to random chance.)
But in a two-sided quick battle, opponents are in equal conditions, and one has the option to "re-roll" the hero's random chance, while the other doesn't.