Disclaimer: This question is of theoretical importance to me trying to educate myself better on cryptographic principles and signature schemes. I don't intend to imply that in practice schnorr signatures are less secure than current 2-2 multisig transactions / scripts.
I am currently reading the musig paper and about scriptless scripts. In my understanding an important common idea in both cases seems to be able to have a single signature produced from several private keys.
Let us assume I can brute force the private key from a public key within reasonable time let's say 1 month (for example because I have a somewhat efficient algorithm for the discrete log in ecdsa (which I don't have). Also assume I can invert the hash function of Bitcoin addresses quickly. Or assume we just know the public keys because I am the third party in an escrow service)
Wouldn't I be able to break a MuSig address within 1 month (under the above assumption) by breaking the aggregated private key to the aggregated public key whereas in the setting of a common 2-2 multisig wallet I would need 2 months in order to be able to provide two valid signatures since I'd have to bruteforce both private keys independently of each other?