I think we are talking apples and oranges here. I am not aware of any useful deterministic model of quantum mechanics. We have no ability to model it as anything other than "random" because we have no ability to measure the internal state of the process.
There are two very different things here. There are tests one can do to ascertain the "finite-state-ness" of a blackbox process e.g. quantum mechanics phenomena. Then there is knowing the state and specific nature of the process inside the blackbox. The first is easy but the latter is generally intractable for many types of processes. Crypto systems are built on very similar mathematical constructs.
Quantum mechanics reeks of being a deterministic process from a "finite-state-ness" standpoint; it is not even of the class of processes for which such things are difficult to ascertain. Unfortunately, this is a kind of zero knowledge proof. Knowing this does not give the slightest clue as to the state or structure of the process, but only tells you that it is deterministic. It does NOT allow you to create a deterministic model of the process, and in fact one can show that for many simple deterministic processes it is effectively impossible to ever build a deterministic model without looking inside the blackbox. We are therefore forced to treat many systems as non-deterministic computationally even if they are deterministic in fact. Nonetheless, knowing that something is deterministic is useful in and of itself even if it doesn't allow us to create a deterministic model.
In short, there are many processes that we must treat as random even if we know they are deterministic in nature. Quantum mechanics appears to be one of the myriad of things that fits this profile. Consider strong PRNGs as an example. Very low Kolmogorov complexity, but intractable to reverse engineer the internal state by sampling the output.
This is surely true; often it's more useful to treat things as random even if we know the deterministic version. On the other hand, QM doesn't seem to be this way at all. I don't think the analogy of QM and strong PRNGs is all the good. (I have published about both.)
The problem is that with a cryptographic PRNG (such as DES or AES or Skipjack) is that the "True State" can be known by knowing the key. In QM, the "key" would also be subject to the QM laws. This has always been the problem for "hidden variable" (or cryptographic like) keys.