Most fans would rather watch a "competitive" 8-8 or 9-7 team than do the right thing and totally bottom out. Problem is, Jimmy's not around to conduct the rebuilding process.
Harris showed a lot of promise in the #3 role last year. Signing Robinson might delay his progress. Of course, you could also sign Robinson to start and put Austin in the slot.
Wilson and Harvin in the same backfield is the stuff of nightmares for D coordinators. As SP noted, Harvin is a proven (if brittle) product, and this year's WR class ain't exactly scintillating.