I'd bet good money that Miggy will give up more runs at 3rd directly, and indirectly as a result of marginal inability over a real 3rd baseman, than he will score.
Ditto for Fielder.
Having a guy with NO glove in the field is a much bigger problem than you think it is. And in the case of Fielder and Cabrera, a ginormous problem.
Remember Giambi? This is worse, and doubly worse again.
Verlander's not going to be winning any Cy this year with a couple of ham-fisted Sumo wrestlers on his corners. Both are DH's, both are worse than having no-one on 1st or 3rd.