I'm gonna play devils advocate here in favor of the trade, just because. That doesn't mean that I'd take the deal, but it's just for some difference in opinion as there isn't any in this thread.
1. Dickey is going to continue what he's been doing for the rest of the season IMO. He's hit gold with his knuckleball. I think there might be something that none of us know about that he's doing, perhaps something revolutionary with his fingernails or something like that, but it's working, and will continue to work. He'll hit some regression I'm sure but will finish top 10 in pitchers I believe.
2: Although Votto is one of the best players in baseball, his fantasy value does not match his MLB value. He hits for a high average but he won't have the kind of impact on categories week in week out like a Jose Bautista or a Ryan Braun. As far as fantasy, he's just not in the same class. Votto'll have 100 runs 30 bombs and 100 ribbies. but so will adam dunn. the only difference is a much higher average, which is very overrated.
Let's hear the rest of your team for some more insight.
Mauer, A-Gonz, Pedroia, Miggy, E. Cabrera, Beltran, Morse, Holliday, Beltre, Gomez, Rizzo, Lawrie, Hanley
Greinke, Johnson, Haren, Hellickson, Jackson, McCarthy, Miley, Anderson, Ryu, Miller, Garza, Street, Frieri, Boggs, Benoit
10 man H2H Yahoo 5x5