While "This phrase is definitely not in the dictionary" is true, every component is. If this sort of password became popular brute forcing passwords would just start using whole word combinations when cracking passwords. i.e a word becomes the equivalent of a character (though from a larger set of characters).

Also wouldn't a hash of a long passphrase be longer? (I am completely ignorant the details of hashing algorithms)... so if I'm cracking a table of hashed passwords, I could set a "passphrase" cracker on hashed passwords of above average length?