What I heard is:
IF you want to end a relationship, just end the relationship. Don't give elaborate reasons. No 'the problem is this, the problem is that', 'you did this and you did that', 'if you had done this, but no , you refused to' etc.
Firstly the reasons should be clear by now, you two DID talk. And secondly, she will try to argue with you and drive you into a defensive position. In an attempt to justify your choice, you might say more and more things that will hurt her more and more. And what is the point, if by now you are convinced that she will not change?
You should definitely encourage her to go counseling, and if she is not the outgoing type who reaches out for help, make sure to inform friends and family so that they will look out for her and take care of her. NOT YOU. It will be brutal for her, but if you try to get out of the relationship as the good guy...à la 'you are a terrific person, I am always happy to be there for you, but I don't want you as a spouse'...you will keep her in a very painful cycle of crisis-consolation-hope-rejection-pain, crisis-consolation-hope-rejection-pain.
If you go, you go. You do not talk the issue to death, you do not look back. You just go. I think someone in this thread said that this is what she did, and I think it is the only right way to leave. There is no explaining to someone over and over again why the relationship will never work. Your wife will hate you, but by hating you, it will be easier for her to get over you. Whatever you choose to do to look good or be the good guy will hurt her even more in the end.