Beta readers are invaluable. And so are critique groups. They show writers the flaws in their books, and more often than not, their opinions and advice should be listened to.
One particular example I have is a character in my current WiP that my critique group just didn't connect with. He was one of those characters that I made up because, in my head, it fit to have a character like him. I fit him in the outline, and he worked as a plot point. But my crit. group insisted that he needed to be rounded out more. He needed to have personality aspects added to him as a character.
But after my first round of revisions, where I DID make him a more important character and played with his personality to make him less of an invisible doormat, I actually saw what they were getting at. He just didn't work. I wrote in a scene where he dies, and there's no emotional impact because he's barely "alive" on the page to begin with.
So what are my options? I guess I could start over. Figure out a few ways to integrate him into the story better. But based on everything else that happens in this book, my best option, in my opinion, is to eliminate the character from the manuscript. Write him out.
Not just because it's easier than any of my other options. I think it'll strengthen the dynamic between the remaining three characters and help them work together when the time comes for them to be heroes. And when they're not working together, the two-on-one will create stronger tension that'll engage the reader and get them to read until early in the morning.
I hope. :)