In some sort of apocalyptic situation, when the absolute fate of the entirety of humanity was dependant on following the correct course of action, I bet Kat would doom humanity because she wanted to ensure they did things her way rather than the way suggested by some scientist or survival expert.
That said, she seems to be doing a good job of getting the target off of herself. The last few seasons of US Survivor, and the first few episodes of this show, have shown us that the social game is important, and the overplayed superfan style is a liability. The last few winners have been the best social player.
The new tribes pose interesting questions. Original Blue have the advantage - they have the two best puzzlers, the strongest female, the two strongest males, the tightest intact pair (Flick and Brooke), and the original 4 plus Nick may be able to make it to the merge, and possibly not even need to go to tribal council at all. And if they do, sacrifice Jenna, or Nick if he gets too big for his boots.
The other tribe is harder to read. Kat seems to be getting the better edit than Rohan at present, so I'm guessing she brings him down - but that tribe kind of need his strength, like Blue did with Nick on the Tegan vote.
Lee is a classic merge boot. And Rohan and Sam fit in there too. If Connor can sqeeze through to the merge he may make it the furtherest of the know it alls.
Brooke is my winner pick at this stage - good position in tribe, in a strong three person alliance, and in a strong pair inside it, of which she is the more likable. Classic BR rules. Also, she is definitely my season crush. The 'island hot' stage has started, and those abs are killing me.