My LS has been keeping track of stats, unfortunately we haven't been keeping track of 1, 2 or, zero horns being broken, but here is what our drop rate is looking like. I find it absolutely ridiculous that the zero drop rate is this high. To note, we almost always have 1 horn broken (if horns even effect drop rate); rarely having both broken.
http://notedls.com/ifritdroprate.jpg
This does track double drops, but even more eye opening are the attendance to item ratio. Some people coming just a couple of times and already getting what they want while others have near perfect attendance and don't have what they want nor as much.
http://notedls.com/ifritattendance.jpg
This is out of 134 attempts.
Ridiculous. Don't know how this hasn't been patched.