if soul sundering causes you to lose soul aetheric density, and therefore make you less alive...
then are dragons more alive than the ancients? they certainly have much more aetheric density than any other creature, to the point that their scales are used as protection against meteion

if being less alive means being able to feel less things, or being at a lower level of consciousness than ancients (such as what animals are like), then that's not properly portrayed, as we can see that the inhabitants of elpis are just... bigger humans
they don't have a higher understanding of the self than what humans can achieve and they don't seem all that different from regular eorzeans in their range of emotions

once again, only dragons are portrayed as beings on a higher consciousness level than humans (until vrtra that is, who is just a human)
yet ascians still wanted to murder them using the allagan empire just as much as they wanted to murder the lesser beings