Impy, have you seen a map of the redrawn IL-08? It doesn’t include any precincts in McHenry or Lake Counties (which used to be the Republican heart of the district). The CD takes in Dem-leaning NW Cook County (but not GOP Barrington and Palatine Townships), Dem-leaning precincts in NE Kane County, and marginal or Dem-leaning NE DuPage County (including the part of Chicago that goes into that county). I would guess that in 2004 Bush got like 45%-47% in the redrawn IL-08; Bush had gotten 56% in the old IL-08. I think that Bush got 43%-45% in the new IL-10, meaning that your hunch probably was correct and the new IL-08 was more Democrat than the new IL-10 only in 2012, not before, but the new IL-08 still has quite the Democrat lean to it, and will be difficult to capture. But then again, Duckworth is a terrible politician, so maybe Goel can let Duckworth defeat herself.
Oops, forgot to include the map of the IL CDs so that you can see the redrawn IL-08: http://nationalatlas.gov/printable/images/pdf/congdist/pagecgd113_il.pdf