But what is made clear in Saurfang's part of the story is that it isn't the battles that he regrets (While he has higher esteem for his opponents than the average orc, that doesn't alter his actions in combat), the three main atrocities that weigh on him involve the wanton and tactically pointless slaughter of civilians in Shattrath, Stormwind (He specifically mentions running down the streets slaying anybody they could catch) and Teldrassil (Maybe two dozen soldiers left up there, every ablebodied soldier being sent down to Darkshore or Ashenvale before then), he did what he could to get civilians out of the firing line in Lor'danel ("Today, we showed them honour")
War is messy business, everybody knows that, even all the armchair-barbarians on this forum, people die (usually in gory as well as noisy fashion, with the complaining of missing limbs and messed up clothes), and yes, there is going to be collateral damage, but just abandoning even the pretense of decency, razing the entire city and going "Kill them all, let Elune sort them out", well, it's easy to see how that might bother Saurfang, or for that matter anybody else who puts any actual value on honour...