Scott Rolen did help the 2012 Reds. I'll refer to when he played some pretty darn good baseball during Joey Votto's injury. Aside from that, Encarnacion's trade value was quickly approaching nil when the Reds dealt him. He got a big arbitration raise in 2010 and his defense at 3B was becoming untenable. He wasn't even the main target for the Jays in the Rolen deal. That was Zach Stewart. Encarnacion was a little bit of salary ballast and a short-term 3B fix.
The Reds traded two arms who haven't amounted to much and a 3B whose value cratered a year after the deal for an All-Star 3B. That's a tidy bit of business.