48/40 doesn't solve problem with this card... Ability should be changed, not cost.
Using sacrifice when You have 50HP doesn't looks well-considered
The ability does not need to be changed. Adjusting the cost changes the minimum damage per turn threshold that this is useful. If we look at two ridiculous minimum damage per turn thresholds (0 or 100) we can see that a 0 damage per turn minimum threshold would be OP but a 100 damage per turn minimum threshold would be UP. By definition any continuous function that goes from OP to UP will have at least 1 point where it is Balanced.
I don't know why You defend this card
This card costed 12/8 (or something like this), 32/24, 40/32, 48/40... We still change cost, so it is sign that something goes wrong with this card. I don't remember more changes with other card. Cost is 4x higher than earier (with the same ability), it is absolutely record. It is like changing cost of Mitosis from 4 to 16
Is losing 48 HP a good against rush decks? Absolutely no.
Higher HP cost SoS= less power against rush. Sorry, I don't understand this idea now. My idea with swapping damage into healing for both players (without losing 48HP) is much better against rush. Shields aslo can do more and faster (against rush). I never used this card against rush. Never. I use it when I see that this card can give me 2-3 turns and I can end game.
But if all this arguments aren't so good for You, then look on Leaderboard in Platinum. Girlsgeneration's deck with SoS has got >200 points more than 2nd player.
What is more - I have no idea how beat this deck. You probably say that I must hold 6 HolyFlash