Brute forcing a key shouldn't be a concern, nor should a known-plaintext attack be. If it is, your crypto is broken. That said, compression before encryption me

Brute forcing a key shouldn't be a concern, nor should a known-plaintext attack be. If it is, your crypto is broken. That said, compression before encryption means there's less data to encrypt, so you win back some performance lost by the compression. Nevertheless, I'm sure the considerations were something else entirely (such as compression seldom being done by TLS).