In my opinion, it would be a great idea to target Wacha. Part of me is probably being sentimental, seeing as how when Adam Wainwright retires, there will be no holdovers from the 2006, 2011, and 2013 World Series teams.
But the numbers speak for themselves. Wacha is pitching like the guy we saw in 2013 and what the Cardinals were expecting him to be when he first came up. I wouldn't say he's an ace, but he's durable and also brings some solid postseason experience with him.
St. Louis must be cognizant of his injury history, but from a performance standpoint, I think it would be a pretty good move.