All this talk of vicous couplings and what to do and what not to do. It is highly unlikely that a siezed coupling would cause one tyre to wear in this way. Wear on the outside only of the tyre with no feathering means in most cases that the camber angle is out. Check the top and bottom ball joints. Wear from outside to in, with feathering too much toe in. Wear from inside to out with feathering too much toe out. Wear around centre of tread, over inflation. Wear inside and outside of tread, under inflation. Wear on outside of tread with no feathering camber angle. That is why when you do a service you should swop wheels around diagonally to negate road camber wear. Not possible on rotational tyres of course you can just swop them back to front.
