Do YOU think we'll get a new Tank and/or Healer in 4.0? And vice versa.

[SendohJin]

Oh BRD+MCH comps are terrible and would continue to be terrible, however that wouldnt be terrible for BRD and MCH players to the same degree as a DRG+MNK comp being viable isnt terrible for NIN players.

with 3 jobs there are 3 non-duplicating combinations for 2 party spots. all the jobs are viable for 66% of the combinations.
with 4 jobs there are 6 non-duplicating combinations for 2 party spots. in your example BLM and SMN are viable for 50% of these combinations, BRD and MCH are only viable for 33% of these combinations.

viable 33% of the time is not the same degree as being viable 66%. 66% is literally twice as good.