hm some small doubts :
- no blood hunt in the sea
- blood is no research priority for ryhleh
especially thaumaturgy + lowlevel construction + mid level conjuration ( accashic + bane lords ) are my ryhleh priorities
- at larger maps can be possible that you have to cross 3-4 sea provinces before you reach the coast and can go out of the sea
big pros of your strat :
-starspawn priests have for 150 gold sacred 1 random , so 1/8 are blood
-starspawns have 2 randoms , so 15/64 probability for 1 blood , 1/64 for 2 blood
-sages are pretty common , 1/8 are cheap lvl 1 blood hunters
-ryhleh are fast researchers + good castlers
with accashic + clams you will have a high gem income though . so i would chose death instead blood on my pretender .
bane lords with soul slay , mind burn , enslave mind , paralyze starspawn artillery will be pretty scary until you reach wish
taking 9-10 astral on your void lord could be cool too . he can wish without empowerment and he can kill off especially marignons , arco's and other races 1-3 astral magicians per mind duel pretty save
but beware of pythium communion arch theurgs . they can easily reach 6-7 astral via that .
you have to be 6 levels above to 100% win and never die .
with 5 levels above you still win 100% of the time but die with 2,8% probability too according to saber cherry's chart .
hope that helps