Let's assume a word list of 7776 words. All words are lower case alpha. The attacker has pur wordlist. And the attacker knows there are seven words in the passphrase.
That's still 7776^7.
Even if we prune the wordlist ("I'm not using 'zerg' in my phrase", "I rolled 11111, that's not random so I'll roll again") it's still not an attackable space.