The problem with Leeming in my opinion is that he doesn't work with Sezer/Austin, he's too dominant and makes them both almost completely ineffective. O'Connor (bar last night), seems to be a better match for them.
Where Leeming is actually very good is tracking through the middle and supporting play around the ruck. In that case, he works well with Cam Smith, and I think we would have done better last night if he played with Smith directing 90% of our attack.
The big picture problem is succession plan for the spine as a whole. Do you get rid of Leeming because he isn't great with our halves, even though there's a decent chance one or both might not be here next season?