Part of the end is bothering me. I've seen it twice.
Why didn't the Aurors have their memories obliviated by the rain like the No-Majs / Muggles. We know the Obliviate spell works on wizards, thanks to Gilderoy Lockhart (Order of Merlin, Third Class, Honorary Member of the Dark Force Defence League and five-time winner of Witch Weekly's Most-Charming-Smile Award). If Scamander had been testing it and found its useful properties, he must have been testing on Muggles, then surely? Bit unethical 
The Swooping Evil potion spreading through the rain was a stretch as it is, let alone it not affecting the magical population.