So, I was having issues with my Lightroom after I updated it a few weeks ago. I went from some super old and out dated version to the one that came out last June. Well, I had to uninstall and reinstall it to get it to stop malfunctioning. Once it installed, I updated it to 6.6.1 and I had the dehaze feature on the last update. Now, the dehaze slider is gone
Dehaze is not part of the standalone version of Lightroom, it only comes with Lightroom CC 2015.
You can refer the below link for your references.