Don't worry about diminishing returns here
To double a creature's power and toughness, that creature gets +X/+Y, where X is that creature's power and Y is that creature's toughness when Unnatural Growth's ability resolves
Turnaround transparency : You want realistic timelines, not vibes
The Best Cards With Split Second Spells with split second tend to cost a little more mana than their more interactive equivalents, so the best ones are either mechanically unique spells or effects that you need to resolve without your opponents' interference
Remember, we can JMA ourselves for ten, not just our opponents
This card can be really nice if you get something busted like Mascot Exhibition, or bad if you hit something that doesnt even work like Teachings of the Archaics