One call to `decryptbypassphrase` for decrypting all columns
No. Scalar operators cannot magically transform themselves into relational operators. You use the ENCRYPTBYPASSPHRASE to encrypt a column (there is no way to 'encrypt a table') and you use DECRYPTBYPASSPHRASE to decrypt a column.

Using passphrases to encrypt the data directly is a very very poor choice. A proper key hierarchy is needed where data is encrypted with a set of symmetric keys and the symmetric keys are in turn encrypted with a certificate. Encrypting the data directly with a passphrase requires expensive size-of-data operation to rotate the keys.