"Thunder Rolls" is not necessarily so morbid. It is all thematic to Ramuh, of course. Who believes that he is just. There is the implication that the old man believes in original sin and probably does not hold that against all, certainly not his children (the sylphs). The refrain would imply that comfort should be taken in some of Ramuh's thematic aspects that aren't so pleasant. Storms, stinging rain, etc. I do not interpret the song as being entirely a righteous condemnation of man.

Seeing those lyrics brought this to mind:

Quote Originally Posted by Answers
Shining is the Land's light of justice (there are just primals, such as the old man)
Ever flows the Land's well of purpose (likely refers to aether)
Walk free, walk free, walk free, believe... (how hard must it be to walk free with the worm of sin spoiling us from within)
The Land is alive, so believe... (from the land we came, to the land we shall return - and that might not be the end)
And then, holy crap, the bridge of Answers...

Quote Originally Posted by Answers
War born of strife, these trials persuade us not (fighting the primals bring no enlightenment nor understanding of them nor their people)
(Feel what? Learn what?)
Words without sound, these lies betray our thoughts (The Echo)

Mired by a plague of doubt, the Land, she mourns (The Darkness within Man, described as the worm of corruption in Rolling Thunder)
(See what? Hear what?)
Judgement binds all we hold to a memory of scorn (The primals pass judgment on us all not just for present transgressions, but for reasons - memories - in the past that we do not know!)
Tell us why, given Life, we are meant to die, helpless in our cries? (If we have brought such chaos to what already existed, why were we created!?)
Musings on what Ramuh brings to the table regards Life, The Universe, And Everything.