['mortal_strike:2'] = {
  name = 'Mortal Strike',
  rank = 2,
  id = 21551,
  level = 48,
  cost = 200,
  replaced_by = { 21552, 21553 },
  talent = 'mortal_strike:1'
},

etc. are not working, Mortal Strike is not talented and the higher ranks are shown as unlearned.

Yes I plan on doing talents differently, just haven't gotten around to them, my thinking was to only check the later ones if the earlier one is trained, similar to how replaced_by works.