Hero's a subjective term, though (see the quote in my signature). I'd look at Toshi, Hidetsugu and Kiku, for example, as heroes. Toshi and Hidetsugu a tad more since they were given more exposure in the novels. But if "visiting evil upon evil" is villainy, does that make the Hyozan Reckoners villains?.
By and large, yeah, it really does.
Actions are not inherently good nor evil, what matters is not the consequences in that respect, but instead the intent.
There can be a heroic action with terrible consequences, and there can be villains acts with fortuitous ones, but in the end it is about the why.
Toshi, ultimately, chose to be a hero even if he was acting selfishly virtually the entire time.
Hidetsugu though? Yeah, he was a villain. His intent was never for the greater good and he slaughtered a **** of innocent people in his mayhem. While that somewhat upset the bigger villain's plans, he wasn't doing it with noble intentions... well, not quite. He certainly had honorable intentions, but those aren't the same as being noble. Of course, then you get into a debate of cultural mores and perspective, but given that we have a third person omniscient view, we CAN actually dictate that sort of thing.
I would define heroism, mostly, by the simple question of if it is selfless and if it improves the lives of those you wish to help.
Visiting evil upon evil, with no concern for those affected because of your own selfish cause is incapable, ultimately, of being a heroic act, even if the consequences improve other's lives.
As I've been saying all along, it is the WHY you do something that matters.