The windmilling vibration loads are still tremendous - the FAA has made Boeing show that the rest of the aircraft can readily handle the blade out vibrations for an extended ETOPS diversion - it wasn't trivial.
The load on engine mounts and wing structure can be significant. For an extreme case- check out whirl mode on the Electra problem/flutter due to 'engine mount ' failures. Sufficient to tear off a wing in a few seconds. Granted the current problem was different in many respects- but the point of high frequency vibrations on structure is real . For low frequency vibrations caused by simple aero loading and what they can do without damping - google galloping gertie.
