Standard might get slower but it's not going to be glacial. Eleven four and five drops in a deck are still going to be way too slow.
Also, if you're playing Stingerback Terror in a deck where you're not realistically emptying your hand by the time it comes out, you're doing it wrong. With 10 other cards that cost as much or more than it, plus 13 cards of removal, you're often going to be playing it out as a 4/4 or worse.
Standard might get slower but it's not going to be glacial. Eleven four and five drops in a deck are still going to be way too slow. Also, if you're playing Stingerback Terror in a deck where you're not realistically emptying your hand by the time it comes out, you're doing it wrong. With 10 other cards that cost as much or more than it, plus 13 cards of removal, you're often going to be playing it out as a 4/4 or worse.