I meant a much more general divination of Nurgle and Isha, not to try to enter his Sancta Sanctorum and spy him...
Well that gets us nothing because the sancta sanctorum is surrounded by divine level wards...the kind Ridcully cannot see through.
We would get no pertinent information to making the spying easier, and nothing on Isha at all.
That thing about Chaos doesn't make sense. Clones have the same DNA but they're different people. They'd be vulnerable to a targeted bio-weapon but they wouldn't have some specific "soul blueprint" that Chaos could exploit, not unless they were raised to be pretty much the same person but being a clone wouldn't be a factor in that regard.
As for the tendency for clones to be inferior, especially at that rate, I call bullshit. In Embers, what matters most is not your bloodline, but who raises you. That's why Jacob was so powerful despite not having any blood relation to Jane. The reason why Syr is so great at war-making isn't because she's our biological daughter, it's because we raised her as our daughter. If the clone of a mediocre figure is raised by a Hero, the clone would almost always far outstrip their genetic progenitor.
Additionally, we have the Sarens to provide proof that being a clone does not result in an inferiority rate that great. Both of them were heroes. If your rate was correct, the chance that two clones of the guy the Sarens were cloned from would both be hero-tier would be infinitesimally small. It's far more likely that them being clones didn't factor into their potential to become heroes.
This was Durin's response to why cloning and mass hypo indoctrination ends badly.
the issue with mass production and hypnoindoctrination is it creates an entire population with exactly the same mental flaws, as soon as Chaos figures out a way to exploit that they can corrupt entire segments of the population fast. In general with the condition of the galaxy and how cloning increases Chaos susceptibility most of the human polities that relied on it have fallen to Chaos by now
Of course its reasonable to assume they would not be subjected to identical indoctrination nor of the same brainwashing intensity the Imperium was so fond of, but they would be physically identical and raised in highly similar conditions expected to perform to similar standards and achieve similar things, which increases their vulnerability and would make them more similar to each other no, whether or not it was intentional.
Clones naturally get -1 to piety, statistically making them inferior on a base statistical level, but nothing that cannot be overcome, after all as you state bloodline isn't what's important training is.
However, not all clones are going to either get the opportunities or due to the warp just won't be as good as each other, if you clone one person a hundred times one of those clones will end up as a Saren (though given that neither of them were especially great) and Pallidus (also a clone, but probably a better example), but the majority of them will end up like Tranth's clones. Perfectly skilled, but when was the last time we heard about any of them?
Knowing this I do not think they would have attempted to mass clone Akadia 1 and would have continued her bloodline through other means (cloning included.)
Regardless since there are literal millions of Lethe's in Callamus, but I'd be very surprised if more than a handful meet the standards for heroes, clones or no clones.