For the Matthew passage:
Jesus is referring to UNBELIEVERS. People who have not accepted Jesus as God. Notice the last line: "I NEVER KNEW YOU." This denotes these "prophesiers," let me think of an example - (Joseph Smith, possibly)are not believers. Heck, even Satan will appear as an angel of light.
It's interesting you bring up Isaiah 59:2 because that's exactly why Jesus came. So we could inherit EVERLASTING life, and not be separated from the Father, God.
Remember Jesus, paid for ALL the sins of believers, actually the sins of the world. Jesus is the bridge over the chasm of sin, over the great "DIVIDE" which brings believers to God.
How can someone or something EVER snatch you out of God's hands? John 10:28