I was just checking Dunn's game log to check this homer tear and saw something interesting. The following is plagued with sample size issues (and other things such as where he was hitting in the batting order). However, I think it illustrates some macro level points that are often missed by people who don't go by Cyclone or Steel, or don't have the interest in digging in to the piles of evidence they provide along this line.
April: .265/.432/.614 (.182 ISO SLG, 17 RBI, .20 RBI/AB)
May: .212/.328/.535 (.207 ISO SLG, 15 RBI, .15 RBI/AB)
June: .221/.368/.537 (.169 ISO SLG, 20 RBI, .21 RBI/AB)
July: .319/.360/.553 (.193 ISO SLG, 11 RBI, .23 RBI/AB)
This does NOT include today's 2-3 with a walk and a homer. A couple of interesting things come up here. Firstly, Dunn's extra base hits don't slump. Sometimes he gets more singles or a few more (or less) walks, but he always hits for power. Secondly, his RBI rate is fairly consistent. Guess what? These things are related.
Even when Dunn is "slumping" and hitting .212 for the month, he still drives people in because when he gets hits, they accomplish things.
Then there's something else to check out, runs. Let's just look at OBP.
April: .432, 25 runs (.23 R/PA)
May: .328, 13 runs (.11 R/PA)
June: .368, 19 runs (.16 R/PA)
July: .360, 8 runs (.16 R/PA)
So when we see that Dunn is on a tear and still batting under .250, let's remember the following 2 points:
1.) Isolated Slugging % = driving in runs
2.) On Base % = scoring runs
At the most base level, these are the two things a player can accomplish offensively and Dunn is very good at both.