I actually agree with this, and the mental burden of where to split the different parts of the multisig is probably the main thing that has prevented me from using it so far. For me (and I think many), coming up with more than one safe-but-hidden location over a long term is more difficult than is often acknowledged.
With single-sig + passphrase, you have only one off-site location to worry about for the seed phrase, and then the passphrase can be portable, stored in a password manager or whatever, just for the case that the seed phrase location is uncovered or there turns out to be a vulnerability in the seed's original generation.
With multi-sig, you have three seeds plus a data descriptor. If the three seeds are kept together, then the wallet can be spent from immediately if somebody were to uncover their location, making it less secure than the single-sig + remote passphrase would have been. So if we wanted to retain the same convenience of the single-sig setup, but with the additional security of a multi-sig against a compromised wallet, then could we keep two of the signatures together in the same location, and then the third signature (and descriptor) made effectively as your "passphrase", kept as portable copies in a password manager or encrypted USB? This is assuming that it is absolutely impossible to spend from two signatures without the descriptor, which I believe to be the case but have not yet tested personally.
In that scenario, keeping the mental location burden the same:
Single-sig 24 words on steel in one location | portable 12-word passphrase (could also be offline, e.g. on encrypted USB)
Multi-sig two signatures 12 words + 12 words on steel in one location | portable 12-word third signature + descriptor (could also be offline, e.g. on encrypted USB/Tails)
There the number of words and data to keep track of is essentially the same, but are we any more secure in the multisig setup to make it worth storing an opaque descriptor too? Unless we want to introduce additional complexity of multiple seed locations, then a strong passphrase may be enough to negate the need for all the extra gymnastics. With a 12-word passphrase typed into a PC on Tails+Electrum rather than a weak passphrase fumbled into a hardware wallet, you basically have the security of a second required signature regardless.
I actually agree with this, and the mental burden of where to split the different parts of the multisig is probably the main thing that has prevented me from using it so far. For me (and I think many), coming up with more than one safe-but-hidden location over a long term is more difficult than is often acknowledged.
With single-sig + passphrase, you have only one off-site location to worry about for the seed phrase, and then the passphrase can be portable, stored in a password manager or whatever, just for the case that the seed phrase location is uncovered or there turns out to be a vulnerability in the seed's original generation.
With multi-sig, you have three seeds plus a data descriptor. If the three seeds are kept together, then the wallet can be spent from immediately if somebody were to uncover their location, making it less secure than the single-sig + remote passphrase would have been. So if we wanted to retain the same convenience of the single-sig setup, but with the additional security of a multi-sig against a compromised wallet, then could we keep two of the signatures together in the same location, and then the third signature (and descriptor) made effectively as your "passphrase", kept as portable copies in a password manager or encrypted USB? This is assuming that it is absolutely impossible to spend from two signatures without the descriptor, which I believe to be the case but have not yet tested personally.
In that scenario, keeping the mental location burden the same:
There the number of words and data to keep track of is essentially the same, but are we any more secure in the multisig setup to make it worth storing an opaque descriptor too? Unless we want to introduce additional complexity of multiple seed locations, then a strong passphrase may be enough to negate the need for all the extra gymnastics. With a 12-word passphrase typed into a PC on Tails+Electrum rather than a weak passphrase fumbled into a hardware wallet, you basically have the security of a second required signature regardless.
Or am I missing something new?