I think it was a bird in hand scenario. Tuch was still just a prospect. Contrary to Wild organization propaganda, the Wild was desperately thin on D. There were only four decent Dmen, the Wild couldn't afford to lose any of the four. So they sacrificed the prospect, which in retrospect was a BIG mistake.
If the Wild had ranked their Dmen, IMO Dumba would have ranked ahead of Brodin. I agree with KA, I would have just bit the bullet and sacrificed Brodin.
You have to remember, the Wild had a pretty good roster at the time and aspirations of contending. Tuch was a future player, Brodin and Dumba were key pieces. They hadn't given up on Coyle, Zucker or Nino yet. Again, Fletcher did not have the benefit of 20/20 hindsight. IMO it's obvious sacrificing Tuch was a huge mistake, but they had Greenway looking like he'd fill the big, strong Forward role.