You have some interesting standards... Vargas posted a .758 OPS in his age 26 season, making him slightly better than league average with the bat. Santana was an all around better player and will likely sign a very large multi-year deal. That's not a C- guy.
I'll simply note that we are talking bench bats here and a part time DH. Santana will want to be a starter, so again, I don't see how Santana makes any sense to this club. I'd be fine with Vargas and/or Park sitting around as a bench bat (though I really want Mauer taking some reps at 3B and RF this spring).
They aren't bad options, with the only real issue being defensive flexibility. With Granite in AAA, Adrianza, and Escobar, I think we are covered if we need defense and want some offense on the bench, so long as we make sure the pen has some better options allowing Molitor to have 5 bench bats.
Some excellent points, except for the Mauer thing.