To be entirely fair, Karkat acts like he's responsible for everyone, not just Gamzee. Which, if he's being the leader of everyone, then technically he is responsible for all of them.

I mean, he even interacts with Eridan in a very pale manner prior to Eridan going all murderhappy.

I do agree that Karkat<>Kanaya is a bit of a stretch as neither are particularly dangerous, but I do still feel a bit that Karkat<>Gamzee did come out of some place not quite nowhere, but in the general vicinity thereof? I can appreciate why people might disagree with it, at any rate. Especially since Karkat does seem strangely way too happy and calm during the entire shooshpap sequence, which, while I definitely get that being his usual ornery self might have gotten them all killed... he still seems just way too happy even when Gamzee isn't looking.

(Also, with what we know right now, the relationship just seems very one-sided. I can't imagine that not getting killed is the only benefit to the more conciliatory natured troll in the relationship. I would think if that were the only benefit, then they'd probably just let the violent one get themself killed or kill them for the good of the species or something. I hope Hussie elucidates more on their relationship in the future.)