Wouldn't it be as unlikely that a deity would reward you for the deeds of others?
Edit:
Well actually, Mormonism is a Christian faith that teaches that salvation comes in and through Jesus Christ, so it really isn't your actions or their actions- but the actions of Jesus Christ- taken on your behalf, that leads to salvation- if you accept it. But it isn't so much a reward as it is an act of mercy.
That same being endorsed baptism by undergoing it himself.
This may seem contradictory, but becomes much more tractable if you're open to the idea that "redemption" is just an abstraction, with multiple inputs, some provideable by Providence, some provideable by others, and some provideable only by the subject in question.
I know I invited 'unlikely' in but let's not make it too welcome or we'll be here all week, or until dang tells us to knock it off.