I really like the little NAA revolvers and I do believe that they are better than nothing. Of course, anything is better than nothing.
I'm reminded of a lot of small game hunting that I have done with a .22 magnum and .22 LR. Anytime I shot a squirrel, it died right away. Coons tended to flop and squirm a while and often required a second shot before expiring. Coons are very tough animals.
Once I shot a big fat nuisance ground hog with .22 mag from a rifle at a range of less than 6 feet because it was sneaking up on it when I shot it. It flopped, squealed and flipped around for several seconds before scurrying back into its hole. I couldn't believe how much fight the groundhog had in him after being hit with a .22 CCI Maxi Mag.
If that had been an agressive attacker I do believe I would have needed a bigger caliber to take the fight out of him.