Harden is a max contract player. He earned it. The problem is OKC has 2 other max contract players, and his role on the Thunder was to provide bench scoring. You had 2 options. Trade Westbrook for a similar deal, and keep and sign Harden to start or what they did. It's a difficult choice to make. I could make a case for going either way.
Martin just needs to be a scoring 6th man off the bench with Maynor facilitating. It will take a while to get it going, but they will be fine. The goods news is they got rid of 3 players that can't play, and added an extra talented player. The trade can't be judged until the picks are used in some way. We will know in 3 or 4 years. Maybe sooner if the picks are traded.