Hi Wally,

A bit more serious sonnet in this lovely poem!

I do not see an issue on my first reading with 'untranquil mist' other than to perhaps place an emdash there to pause before reading 'our wisdom bars'.
Here are just a few thoughts below to ponder as you wish...
QUOTE
The tour is far, the route adverse [Perhaps: The journey's far - for a bit less abrupt sound?]
our quests beset with balk and woe.
Most outcomes of our toil obverse
and greed shall tax what seed we sow.
Today, great rivers test our mind
that desert plains tomorrow be
lush pastures vast and unconfined;
more fertile than the plundered sea. [I love the closing couplet here!]
[For the below stanza- I suggest changing as follows:
Delete the comma at end of L1, use semi-colon at end of L2, start L3 with 'A' instead of 'at' and replace 'untranquil' with 'untranquiled mist-'. In L5, perhaps replace second 'dreams' with 'fate'?
Love the closing line!] 
Tomorrow's walls we need transcend,
should man aspire to touch the stars
at cost mere kings can't comprehend
untranquil mist our wisdom bars . . .
Whilst dreams yet dreams may long remain,
we'll dream our God-games just the same. Enjoyed the read!
~Cleo