First off, my expertise (such as it is) does not include rotor dynamic vibration, but I think having the plane of the IPT disc directly over the aft IP bearing (i.e. zero overhung moment) might have some advantage re whirl mode. But I have never seen this arrangement employed before.
Second, I wonder just how accurate the flowpath detail in Turbine D's cross-section is, especially in the IPT > LPT area. I could see where the inner band of the first LPT nozzle stage could contact the IPT blades at the TE root, perhaps initiating blade failure. This would seem to be in conflict with the failure sequence in the powerplant report. I think Lyman is in agreement here.