I agree with the suggestion to reduce oz offered (whether you dilute or just give less, I've heard of success both ways).
We just started having DH go in to do the night feedings. DD was still doing 3 am and waking up around 6. I was nursing, and basically couldn't go in or she'd insist on nursing. One night with Dadda, and she stopped waking at 3 am. (Dadda is VERY proud of himself). I think she just had to break the habit with me.
Now, she wakes around 5. DH gives her a bottle and she goes back to sleep until 7-ish. It's a miracle! We're going to have to tackle the 5:00 bottle next - I think we're going to try diluting it.