Salvage is interesting, but I believe this card will be a niche/fun card like reflective shield. The main problem I see is that the most powerful permanents are all slow. Having yet another slow card to protect your slow permanents is going to make you even more delicious to rushes. The other side of this coin is that this card is useless to rushes which often have no permanents, or don't rely on their permanents.
If salvagers had middling attack then they might get used in rainbows, but I don't think their utility is enough to justify 0 attack.
I personally think these cards would be much more interesting with a middling to strong attack in addition to their niche ability -- somewhere between mind flayers and spiders.
But maybe we will see one salvager in a deck that countains 3-4 permanents and a large number of creatures. The idea would be that the enemy will have more important targets for CC than the salvager, which will allow the salvager to keep the permanents in play. Without the salvager, those permanents would get eaten by the enemy's typical 3 PC.
I guess this salvager might be pretty nice in combo with cloak (except vs. steal
).