Dallas should have offered to take Chandler off the Knicks' hands using their cap space or even doing to the Calderon/Felton swap. But if they went the PG route, they should have tried to get an asset out of New York, or at least not given up a few themselves.
This is as bad as the Bargnani trade from a leverage standpoint, although it's obviously better from a personnel/value standpoint. Dallas can certainly recover by signing a PG like Lowery and picking up a small-forward like Ariza with their cap space. But they still messed up this part of the off-season.