You should note that in LA, Growth-3 stabilizes your population against the effect of your dominion. Cancelling population loss is a bigger deal than increasing population growth
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I've never noticed a difference for the two turns less of paralyze damage, and have found Illithid Soldiers to be quite effective troops.
Note that LA R'lyeh can also recruit units on land.
The various lesser hybrids - are dreadful. You'd rather have independent infantry.
OTOH, the hybrid assassin *is* a nice unit, and since you can't recruit real illithid on land, you might as well grab them.
Void cultists are at least cheap, and can help lead piles of freespawn around.
Have you checked MA R'lyeh on land? Do they get land units?