Anyway, I'm starting to theorize trolls as a whole are much less bloodthirsty than they -try- to be. Like humans and money.
About half of them are dead now because nobody was watching to make sure they didn't kill each other, and they started killing each other. As incompetent as Karkat first appears to be it's obvious that when he's distracted by something shit starts falling apart at record speed.
Honestly, 11 of the trolls are absolutely normal, but Vriska's spot on in saying that Karkat is more human than troll. Besides having the giveaway blood, there's the fact that he's the
only troll that exhibits the human trait of altruism. All other trolls that seem helpful are either trying to manipulate a victim (Vriska, Terezi), expecting something in return (Kanaya, Eridan), or only friendly as long as you belong to their "team" or otherwise don't piss them off (Aradia, Nepeta). Karkat is the only troll anywhere on the spectrum to be able to look past his own petty grudges and work towards the greater good. It's such an alien concept to the other trolls that the only way he can get them to accept it is to be as obnoxious as possible about it until they just do it out of frustration.
Anyway I suspect that this trait is what Karkat initially
thought he saw in Terezi and why oh wait a minute there's an update and oh god what twelve more trolls
oh god it is Bleach!