I shot a few bucks with Fail Safes, the bullet the XP3 replaced. I've been told the XP3's will expand better, don't know if that is true or not.
I didn't consider F/S ideal for whitetail and had the same results you did. Little hole in, little hole out, even hit shoulder on one, but they all died...
I got a bag of 'em in 7MM from a friend and used 'em just to see what would happen.
They did do a great job on big Russian boar though.
JM