If the primary goal was to save the bullpen, he should have let Affeldt pitch another inning. If the primary goal was to win the game then pulling Dunn was a bad move. And to top it off he was asking Burton to do something (pitch 2 innings) that he had never done before at the ML level.
The pitcher's slot was not guaranteed to even come to bat in the 6th inning. Dunn's slot WAS guaranteed to come up later in the game. How dumb would this move have looked if the Reds went down 1,2,3 in the 6th or if Burton couldn't pitch 2 innings?