I think it helps complete him as a main eventer. He needed a good submission move IMO and since the torture rack is "taken" I think it's a good second choice. He needed a good way to make opponents tap out, and he found one... though I wish he had debuted it against someone seen as a bit "tougher" than Santino.
I think the move would be better suiting for Mcintyre then Sheamas.A submission finisher dosen't fit Shemaus and he has enough finishers/Signitures.
I actually didn't think about Drew McIntyre, but I agree.
Sheamus already has 2 finishers. The people who would've benefited most from an added finisher imo are the guys like Wade Barrett and Drew Mcintyre who only have one finisher and actually need the added depth within their moveset.