There are no major noticeable flaws, but to prevent problems, it will be uniformly considered for play
The real issue with Natural Order is that you have to get something that can resist removal else you put yourself down too many cards to recover well
The deck then adds a number of creatures and spells with proliferate to quickly multiply poison counters including Atraxa, Bloated Contaminator, Ezuri, Norn's Choirmaster, etc
Some people just want one
Magda, Brazen Outlaws abilities give players an extra source of mana and an easy way to search for the cards they need at any given moment
A 4/4 with flying and infect for 5 mana is a huge threat, especially when you can swing the turn it hits the field by giving it haste