Did we "need" him, no. But any time you have the ability to grab a top-notch starting pitcher, you do it. Especially since it also keeps him away from your compettitors in the division. We won't be able to fully judge this trade for several years, at the earliest. We have to see:
A: What Sale does for us. Wins, WS appearances, etc. And of course, health. If he stays healthy and dominates and we win at least 1 WS. it's worth it.
B: What the prospects end up doing for Chicago. If Sale does nothing and the four end up being HOF performers, that would suck. but I seriously doubt that happens.
We simply have to wait and see. I personally think it ends up being a win for both organizations. We shall see.