One of the weaknesses of dredge as a mechanic is that the dredge parameter is not something you can change from 2 to 3 or 4 and clarly are able to say whether the card becomes better or worse with increasing the number - its not a developmental valve for balancing.

Salvage is the same. Salvage 0 might be the best for you, if you just want the card already in your graveyard, or salvage 4 might be uch better if you primarily want to fill your graveyard.

The most concerning thing to think about is a salvage deck, that actually knows how to filter the graveyard of lands and other cards to just to recycle salva´ge cards over and over.

I feel "dilluting" the graveyard with random cards from the library is just creating the illusion of balance. I'd hate to be faced with this mechanic in play design.

All Salvage cards were created with the intent to fill the graveyard. I will reevaluate the cards that would affect graveyard manipulation. Erased in Total may be a problem, but it requires you spending four mana to counter your own spell, which seems very janky. Grave Pauper is probably the biggest threat. Thrashing Enforcer was created with the idea that it would hit the graveyard from being salvaged in the first place, and is additionally only itself. Whispers From Beyond is probably fine as it's only a single creature. Highway Cannibal is probably the second biggest threat as it's ability can occur each combat, though Highway Cannibal is in red and meant to play with Marytr cards that ended up in the graveyard. Heroic Spirit would be the third most problematic, but needs to be cast repeatedly, so I rank it below Highway Cannibal. Jungle Snapper can remove itself, making it a Thrashing Enforcer for green.

Oh, but Salvage was created to help out Recycle, so there's all 15 (potentially more) cards that can filter the graveyard.

Moreso than the salvage number though, I generally increased the CMC to something higher than what the base cards effect would be, ex this costing more than Inspiration. To what degree that will affect play I do not know.