chance to miss is a random thing, thus it belongs more to 
, but i like your idea of one salvager being able to only recover a permanent a turn, wich indirectly makes the player wanting more than just 1 copy of the card in the field. basically the more there are, the more protected you are
EDIT: maybe giving him an ability to protect a target permanent you control, a zero-cost ability (because PA only costs 1 and protects permantly) but make it burrowed, halving its attack when its protecting the permanent. just an idea
Yes, randomness is more of an entropy thing, but fate egg is random and purely
... But the chance to fail is just an example. As long as a single salvager won't protect every permanent in your possession indefinitely it will be all good. That's my main concern, so anything to that effect works for me.
Plus, like you said, it will encourage the player to have out more than one at a time.
So maybe something like:
"Salvaging:
Return permanents you own to your hand if destroyed, up to N times per a turn."
Where N can be set to whatever the author / community thinks will make it well balanced.
