Honestly, its just sloppy writing.

Earlier in the season Carol is as practical and able to kill as much as any of them. That's the very thing she butted heads with Morgan over when he took that Wolf hostage. But now she loses it and strikes out on her own because she just can't do it anymore? C'mon. Where and did this sudden turnabout originate? Sloppy!

Then you have Darryl, one of the smartest, most capable survivors in the group suddenly go off on his own to avenge the chick that got the arrow through the eye? Even if he wants payback for being tied up and his bike being stilen, he's going to be smarter than just riding off on his own. And then he let's Dwight get the drop on him so easy? Sloppy!

And to top it all off, the others follow them out there and allow themselves to get separated, 1 here, 2 there. It's just unrealistic.

They batter not kill Darryl, especially since it's Glenn that gets the bat treatment from Negan in the comics.