Is there a position prospect other than turner who you expect to be playing any time soon? Most of the farm depth is in pitching not hitting - hitting is turner and a bunch of guys in A ball you're hoping turn out; I'd give up any of them to know that you have a hitter like Donaldson for the next three season (if we're just talking about 2016-2018 most wouldn't even factor into the conversation).
That's my exact point, as I said above I would love to flip Ward/Kieboom/Difo and even Cole, all four of those guys for Donaldson. But I don't think that would have been enough, because most of those guys suck. Throw in Victor Robles, Jason Reetz and Pedro Severino, give up all seven of 'em for Donaldson, outfield is locked for a while anyways, just sign Matt Wieters to replace the catching problem.
Toronto gave up three major-league ready players including Brett Lawrie, their every-day 3B and Kendall Graveman, who has a 3.86 ERA in about 100 IP in what is his rookie season. They also gave up Franklin Baretto, a SS who is now Oakland's #1 prospect.
They essentially gave up Joe Ross, A.J. Cole, Michael A Taylor and Trea Turner. That's not an perfect example, but I think it evens out cumulatively. That's a hell of a lot for Donaldson. If we had more depth at middle infield and outfield, maybe you make that trade, if you're willing to sign some free agent pitchers. Otherwise, damn. I think people underestimated the haul Donaldson cost.