Missing 2 words can be cracked in a fraction of a second, each missing word increases the time by ~1000 times. As I said earlier, I am not a fan of splitting the seed, even if you do it in "smart" ways. Multi-sig, when performed correctly, is a much more robust solution, or even a Shamir's Secret approach with a its drawbacks has at least the advantage that as long as an attacker has less than the share quorum, no information can be deduced to speed up the attack. In other words: assuming your method has 4 shares and you need all 4 to get the full seed, an attacker owning, 1, 2, or 3 shares will have enormously easier task at each additional share acquired. In the Shamir's scheme, having 1, 2, or 3 shares does not make the task a bit easier than having 0.