Viera are extremely different of the Miqo'te...
other point the male mithra was existing, simply extremely rare and hidden. for the miqo'te it was never clear, since they are not the mithra.

about possible link with ivalice, i recall perfectly lahabrea saying something about "dimensional rift are open now". without forget we don't know what are the race on the other continent of isalbar and the third one!