I've been doing some testing, and I've made it to 1303 points and #179 on the ladder in a short matter of time with these changes:
Scarf Adamant Terrakion in the last slot with a moveset of SE/CC/X-Scissor/Rock Slide
Tinkerbell Celebi with HP Fire swapped for Virizion
Jirachi with Fire Punch, Stealth Rock, and Body Slam
The team performs very solid against most other teams. I typically lead with Rotom-W, trying to gain momentum, or Jirachi, trying to set rocks early, because rocks are a vital factor to this team's success. Celebi acts as a great lure and eliminator for both Scizor and Ferro. The team struggles with Sub Protect Gliscor (Gengar is the only member that can readily deal with it), MixMence (glad there aren't many of those), Any Haxorus (who doesn't), and SubCMRachi (usually have to resort to rking with Terrakion) among others. Overall, a very well constructed team, and Nidoking certainly pulls his own weight.
Edit: Yeah, so I'm changing my vote. I tried Gyara, but not having a spinner and a lack of reliable recovery really hurt it. Celebi fills its role admirably, as well as giving the team some great immediate power with Leaf Storm.