I didn't think Tracey did too bad a job against the Panthers. He has a bit of "deer in headlights" about him, but his defensive positioning, kick defusal etc. was generally pretty good. I reckon for someone who got switched in to the spot on the fly against the best team and kicker in Rugby League, he was a solid C+.
As well as he does it, WK's role in the backline is pretty simple from a tactical PoV. Everyone else is there to try to give him a 3-on-2, and he is good enough most times to execute it. Tracey doesn't have that touch, but I don't think Miller did either. Atkinson probably does, but then he won't be as good as those other things that Tracey did well. Everything is a compromise.