> I wonder how much time that would take to crack on modern hardware...
A very long time. You're still looking at a total of 3-5 words you need to guess (9-25 characters based on 3-5 letters per word), in the right combination, and assuming all words are English or popular colloquialisms...
("greatly reducing" is still not going to make brute forcing a realistic choice).
It would still take a very long time but remember we're not iterating by character anymore. Each word is a 'character' and our alphabet is the english dictionary.
So for the example above, we have to guess 5 slots in the passphrase and each slot has [number of words in english dict] possibilities. And also we'd probably start guessing assuming 2 word passphrases and have to exhaust all of 2, 3 and 4 before we start guessing 5 word combinations.
A very long time. You're still looking at a total of 3-5 words you need to guess (9-25 characters based on 3-5 letters per word), in the right combination, and assuming all words are English or popular colloquialisms...
("greatly reducing" is still not going to make brute forcing a realistic choice).