Mavs were just blowing by Perk, especially in the first half, for uncontested layups. To Perk's defense, he's not fully recovered, but still he should be able to cause some mis-direction or altered shots. Collison and Ibaka are much more valuable to OKC at this point.
I don't know if we necessarily won the trade, but I don't think it's an obvious loss. Perk wouldn't have put us over the top vs. Miami....though Shaq may have.
What really matters is who we can get next year, presumably for the MLE, to play the 5.