Yes and no, hence my choice of the word agnostic.
We *know* salvation is to be attained in the Church, the Ark of Salvation. Some within the Church in this life may be 'washed overboard' by their sins and the passions, and it is dimly possible that those clinging to the driftwood of other creeds may be saved by Christ's grace in a means unknown to us. We may even pray for it--on Pentecost we Orthodox pray for the renewal of all of creation, yes even the demons!
But we do not know that Christ's grace is operative outside the Church in any way which will suffice to save anyone, save by leading them to the Church. Thus, we must evangelize even those who adhere to morally noble non-Christian creeds or heretical variants of Christianity. (If moral nobility sufficed for salvation, Christ's Incarnation, Death and Resurrection would have been unnecessary, and Pelagius would honored as a Father, not anathematized as a heretic.)
Oh, I agree 100%, and Pelagianism is of course utter nonsense.
In the Latin Church we keep the feast of St. Emerentiana, who died a catechumen martyr at Rome. That she can be venerated as a saint shows that God is not bound by the sacraments He created, even though they are his normal means of salvation.
Rest assured, I wouldn't DARE to allow anyone to rest comfortable in the notion that they will attain salvation outside the visible Church. Because the moment that you think that, you've already made a conscious (and sinful) decision not to enter and not to receive the grace of God.