Let's face facts: the e-brake is not primarily designed for off-road. It's a legal requirement that has application when parking. In an off-road situation, if you are in 4HI or 4LO, and anything on the rear shaft, pinion, axle, etc. breaks, you still have the front axle holding firm--assuming you have the vehicle in gear w/clutch out. Correct? I've yet to see a land cruiser pinion, shaft or axle grenade on the street OR grenade BECAUSE of a drive shaft mounted e-brake. Well, this is just my experience and I'm sure there are others out there. Don't get me wrong, I set the e-brake when stopped off-road also; however, that was not the reason Toyota put the thing on the truck, IMHO.
The one thing I don't like about the e-brake being on the rear axle is the necessity for the cables. They are pretty exposed--especially if you back up and strike something. There are any number of ways to look at this but I guess what I'm saying is that I've got no problems with either setup. I've got vehicles with both and never had either one fail on me.