Kat was not in the original alliance of 5 so she was expendable when Tina's daughter arrived. It was also good to get rid of her because she still has a loved one on the other side. Basically what Tyson is trying to do...eliminate those people who still has a loved one on the other side. That's why as long as Vytas is around, Aras is Tyson's target. Now that Kat is gone, Haydn is no longer a threat too. Now if they are smart, they need to split Tina and her daughter. As for the Redemption Island, they should all be rooting for John as he is the only one who doesn't have a loved one still playing.
If Vytas were smart, knowing that he was going home and knew some of the clue to the HII. He should be desperately looking for that HII like a Russell Hantz. At least make it look like that he is looking for it to make the girls paranoid. If you can't find it, make up some HII then put it in your pocket and make it obvious to make it look like you have it.