Perseverance of the Saints vs. Perseverance of the Elect?

The more I read Scripture, the less I am sure of the doctrine of the perseverance of the saints. The issue is that whenever you see someone fall away from the faith you basically have to say that they never had saving faith to begin with. There's room for apostasy, but you are forced to deny apostasy in the literal sense of turning away from genuine faith. I have just recently heard of the Augustinian/Lutheran idea of perseverance of the elect, which separates justification from final perseverance. The idea is that God is able to give someone the grace of faith without he grace of continuing in that faith all their life. Those who are elected to final perseverance are those who will be saved in the end. This makes the "warning passages" in the New Testament seem more genuine, as well as the apostasy throughout both the Old and New testaments. You aren't required to say that that kind of apostasy is really apostasy from a hypocritical or weak faith which lacked the indwelling of the Spirit. This doctrine also coincides well with the passages which suggest that God will definitely and without fail finally save all who he intends to by his divine election. What are your thoughts? What Scriptural reason do we have for thinking that justification and perseverance are inseparably tied together?