I think borksen is indeed genuinely want to join the team not because of contagion. It's cause of the entire game make her think she can confidently handle heil-ly. From the start, she was never seen among her classmates. She works alone while giving advices to their classmates. She knew tserri can't be redeemed (probably).
Tserri is indeed genius and looks unbeatable already as of now. But for now, his ability to read future has a weakness because of his zetsu state.. this ability is indeed scary in his hand but it has limit that only he the one who can move in his future-seeking ability. I mean, he can be dealt with (after his ability being known) by a layered plans. He can't beat a synchronous army by himself. But it's still be very very difficult tho
This is why i have a wild guess about the future plot:
1. Heil-ly will join a collaboration team with kurapika
2. Kurapika need to do that because the other hunters already too busy protecting their own prince
3. Kurapika need to do that because his ability is very limited in a war. He will definitely in his attempted surprise attack but with the exception of 4th prince's zetsu ability. Kurapika will absolutely lose if he go 1 vs 1 to tserri with or without surprise attack
4. Heil-ly will be redeemed not because of borksten. Queen oito will be successfully convince her. Queen oito is a strong character even though she is just a normal weak people
5. Number 4 will be possible due to the status of morena is not the real morena and queen oito's background is from a poor family
6. Tserri's future seeking ability will get stolen by chrollo. But because of his talent, he will get another hatsu by different method. How is that possible? It's because of his weakness that he can't make a friend (he doesn't believe he need friend). Chrollo will take advantage of this