Let's just assume right now that the A's sign Billy Butler. The roster then baffles me:

v. LHP:

C: Norris
1B: Blanks
2B: Punto
SS: [Whoever they sign]
3B: Donaldson
LF: Gentry
CF: Crisp
RF: Reddick
DH: Butler

v. RHP:

C: Norris or occasional backup
1B: Jaso
2B: Sogard
SS: [Whoever they sign]
3B: Donaldson
LF: Moss
CF: Crisp
RF: Reddick
DH: Butler

That makes use of 13 position players, which is what the A's are presumably going to carry. Which means that anybody not listed above is S.O.L., which specifically means Stephen Vogt and Sam Fuld. Now what you could do I guess is say that Vogt is your other catcher. Do you want to do that? I'm not real sure you want to do that. But I guess if the roster makes you do that, and you've been putting up with John Jaso anyway, then you do that. In which case you don't need to sign a backup catcher (beyond the one or two you need at Triple-A).

So the addition of Butler basically means no Sam Fuld, and the set of comparisons becomes:

Butler offense v. RHP > Fuld offense v. RHP
Butler offense v. LHP > Jaso/Moss offense v. LHP
Moss LF defense < Fuld LF defense
Jaso 1B defense ?<? Moss 1B defense

I think this is probably a net gain overall, and as long as Vogt really is your second catcher, you've still got the flexibility to put him and Blanks in outfield corners, Gentry's still around when Crisp gets hurt, and so forth. It all seems like a marginal gain for $10 million per year for three years, doesn't it?