If you include Indexing you have to include The Maker’s Eye.
I don’t include either for the same reason I don’t include Legwork: They aren’t a win condition by themselves.
But wait, you say, didn’t I include Account Siphon and Vamp? Yes I did, and I feel they’re the weakest of the threats I listed as they’re answered with more than just ICE. Similarly, Indexing, Legwork, and TME are answered with more than just ICE. Bhagat, Keyhole, Temujin Contract, and Medium have a couple of answers besides ICE, but by far the best answer to them is icing up the threatened server.
This isn’t to say that Indexing is a bad card, far from it. Just that I don’t feel it’s a legitimate threat that the Corp must answer and deal with, or lose. It strikes me as a Legwork-like card, or Notoriety. A card that enables you to have a Power Turn and do something Cool on that one turn.
Boils down to threat and answer are subjective, and in my opinion, Indexing doesn’t rank as a high threat the way that the other listed cards do. Partially because if you play an Indexing, the Corp’s first reaction isn’t “Guess I should defend that server” but instead “Well, that just happened, let’s hope it isn’t too bad, as I continue going about my game plan.”