The goal in Survivor should be to get in a majority alliance AND be in a good position in that alliance. We saw how well being in a majority alliance worked out for Denise and countless other players who were at the bottom and didn't make a move. And ultimately that, above all else is what caused the downfall of the Onions, not being 'screwed' by a twist. The fact of the matter is that even if they merged at F10, they were in trouble. They made it too obvious to Susie that she was not in a long term position with them.