1. How do you know you are ahead of or behind the OHJ traffic unless you can see it?
2. Yes, OHJ traffic joins at the same height, but opposite direction joiners are horizontally separated by the length of the runway.
3. You don't have to "fart around turning umpteen times" if joining in the overhead from the deadside (unless umpteen = 2). You turn once in the overhead then into the deadside descent, always turning in the same direction as the circuit.
The safety of all joining arrangements at uncontrolled airfields is dependent on traffic making accurate and informative radio calls at the correct point, and everyone listening out so that they get a good picture of the traffic. I find not enough people ask for more detailed traffic info - e.g. if you want to do a direct deadside join and you know someone else is joining but aren't sure exactly where they are, why not ask? Very few people do in my experience.
The bottom line for me is that the safest option is to have a STANDARD way of joining which everyone understands. OHJ isn't necessarily the best or only way, but it's a lot better than having everyone using different methods of joining, many of which are completely unknown to others.
NS