I'd actually say it's probably generally worse than Sanguine Bond, though this is coming from the perspective of someone who mostly plays 1v1. Lots of heavy life-gain strategies are built on blood artists and soul wardens, and this doesn't get those. I'd probably cost it closer to 1BBB or 4B, slightly easier or cheaper to cast than Sanguine Bond, but not much. I also second Thomas Cardew's suggestion of Zero Sum Game, which is much better than anything I had come up with.
As a point to templating, I would remove the "at once" and clarify that it only occurs if all of the life is gained as a single instance in reminder text.