How to explain the Mystery of the Atonement has never been a "core principle" of the Christian faith; the core ideas of Christianity are pretty well agreed upon as contained in the historic Creeds. There has never been a dogmatic statement on any one Theory of the Atonement--what is agreed upon is the Atonement itself--that Christ reconciles the world to God.
That's not really germane to Christus Victor itself, as Christus Victor is about the significance of the Atonement itself; this question is really more of a soteriological one and depends on one's soteriological view. As a Lutheran I subscribe to the Lutheran teaching of Justification by Grace Alone through Faith Alone; the quote from the Large Catechism in my previous post largely covers the Lutheran position: Christ's work is appropriated to us by the Holy Spirit through the Means of Grace (i.e. the preaching of the Gospel) which creates and grants faith to us apart from ourselves. Faith is the gift which God creates in us through which He appropriates Christ's work and His gifts; faith here is something that comes from outside ourselves, from God. Insofar as it is God who works faith in us by the preaching of the Gospel, apart from our own will or efforts, and it is faith through which we benefit from the promises of the Gospel then yes faith is required. Because faith is God's work in us to make us His own, unite us Christ, etc.
As a disclaimer: This should not be taken to mean that any who don't have faith, such as those who have never heard the Gospel, are damned. That isn't what is meant by faith is required. Lutheran theology makes a big deal about confessing what is normative, ordinary, and revealed and trying to stay silent about what is not revealed, or what may be extraordinary. A Lutheran, for example, can't say that unbaptized or unborn children aren't saved because we have no basis to say anything one way or the other on such a topic. But that faith is the working of God in us to turn us toward Himself in His own kindness by the power of the Gospel, that is what is revealed and that which we can affirm in the positive as a statement of faith.
A human sacrifice doesn't defeat evil. But the Christian teaching on the Harrowing of Hell is that Christ--on account of Who He is--has destroyed the powers of sin, death, hell, and the devil. In death Christ died, and swallowed up in death descended into Hades and there despoiled it.
St. John Chrysostom's Paschal Homily is helpful in articulating this particular Christian doctrine:
"He has destroyed death by undergoing death.
He has despoiled hell by descending into hell.
He vexed it even as it tasted of His flesh.
Isaiah foretold this when he cried:
Hell was filled with bitterness when it met Thee face to face below;
filled with bitterness, for it was brought to nothing;
filled with bitterness, for it was mocked;
filled with bitterness, for it was overthrown;
filled with bitterness, for it was put in chains.
Hell received a body, and encountered God. It received earth, and confronted heaven.
O death, where is your sting?
O hell, where is your victory?
Christ is risen! And you, o death, are annihilated!
Christ is risen! And the evil ones are cast down!
Christ is risen! And the angels rejoice!
Christ is risen! And life is liberated!
Christ is risen! And the tomb is emptied of its dead;
for Christ having risen from the dead,
is become the first-fruits of those who have fallen asleep."
The idea here is rooted in the doctrine of the Incarnation, St. Gregory Nazianzus states, "Whatever is not assumed is not healed", what has been united to Christ's Deity is healed--therefore Christ, being completely human, completely heals humanity. Thus in dying Christ-God participates and unites Himself to human death, in dying therefore He submits Himself to our universal mortal fate: Death. It is in His rising that He defeats death, because He has conquered it. He is swallowed up in death and then three days later defeated it. And therefore, in Him, by our sharing in Him, we have the promise that we will likewise be raised up. That is the Christian hope, the future resurrection of the body.
-CryptoLutheran