His BB% is up +2.5% from 2011 and his BABIP sits at 0.326, so that suggests he's getting a tad lucky but at least he's picking his pitches better this season. He still swings and misses more than most and is on pace for 123 SO this year, but the SO are just part of the package.
I think his value sits at mid-3rd round if he can play 3B in your league. I feel a lot of people believe he will regress quite a bit next season. He's never had much hype around him and now that the Angels have Pujols and Trout, Trumbo will be getting even less attention. His peripherals suggest he's made a slight improvement this year, but 0.250 to 0.300 is quite the jump. In 2011 his BABIP was 0.274 so that combination of a slightly better approach at the plate and luck has really benefited him.
0.270 with 35ish HRs sounds about right, which for 3B eligibility is phenomenal. I predict he'll be taken somewhere in the 4th round just due to the fear of regression and lack of attention compared to Trout/Pujols.