Hi!
I am not sure how stealing techs works.
In DL you spend ~2500 BC per race to get to advanced espionage, and then you just wait for these rare moments when the tech will arrive. In DA you need 5 spy/weeks to get the first level of espionage, unknown for next three levels (I never bothered counting). While you have at least one spy active on another race, it has a very slim chance to steal a tech. I don't know if after reaching advanced level there's possible to steal a tech even without active spies.
I have great spy%.
In DL great spying bonus is helpfull. It decreases the costs of spying. In DA it just helps you to spend MORE on spying == you get a spy faster. Since each spy costs significantly more to train, and the 20th spy costs as much as a fully armed huge ship, is spying beyond the first level IMO silly. Keep just some spies for defenses, and invest the saved money into something more usefull.
BR, Iztok