Check Plouffe's minor league statistics. I think he has had power for a number of years. It just has not translated well his first few call ups. As for the average, again, he hit in the minors but not the majors. I have not watched enough Twins games this year to say what is for real or not. Objectively, I would think any of those outfielders are overpays unless you take account of position scarcity and contracts / draft position (if it is a keeper league).
