I don't think Riley had a choice (all three or nothing) and I'm not so certain that Bosh is the worst fit of the three but max money for a no D no pass/no vision post player is not a recipe for success (as we know). You had to figure having LeBron and Wade on the wings would negate most of Boshs weaknesses but they seem to be stepping over each other on O and vacationing on D.
I'm with the Sportguy in that I see Bosh being traded within 18 months for pieices that fit better (interior D and 3 ball sharp shooters). Personally I think dealing one Wade or James would be more fruitful...outside of Kobe and Durant you could ask for any player in the league AND more. The new CBA may also force the issue, so what moves do you think Riley mnakes if the struggles continue.
For fun: here's Pat Riley in "The Hangover"...