Setsuna and I were discussing this on IRC and came up with a few suggestions for you.
I'd like to see a Life Orb + 3 attacks Rankurusu mention somewhere, most likely in Optional Changes. Thanks to Magic Guard, Rankurusu doesn't take any recoil from Life Orb, entry hazards, and weather, making it a fantastic Pokemon to utilize LO + 3 attacks. Rankurusu doesn't always need Calm Mind to plow through teams, so giving it the option to run an extra coverage move is a good idea, IMO. The set would likely contain the following: Psychic, Recover, Shadow Ball, Focus Blast, with a Modest nature and 252 HP / 252 SpA to take advantage of Rankurusu's reasonable bulk and amazing offensive capabilities.
I'm glad you added Thunder Wave as option here. Though, I'd like you to explain its use better. Currently, you only say "
Rankurusu can run a Bulky set which sets up Dual Screens or Thunder Wave but with it's typing is much better suited to having a more offensive role." I would much rather see you say that Thunder Wave can help slow down opposing Pokemon, which helps Rankurusu since he's as slow as can be. You also should mention that Thunder Wave makes Rankurusu a great team supporter, as it can slow down some of your opponent's 'mons for your other team members to take advantage of.
- Scizor and Blissey will not appreciate Choice Specs limiting their options.
Please get rid of the Scizor mention. Plenty of Scizor run Choice Band as an item, and if you Trick your Choice Specs onto it, you'll be locked into a move, giving Scizor an ample opportunity to Pursuit you to death.
Lastly:
I've used CM + Recover Rankurusu extensively and I can say that Bold, 252 HP / 252 Def, Leftovers is by far the best option. Psycho Shock is completely pointless when its only use (outside of something far fetched like beating CM Suicune in a CM war) is to beat Blissey. Blissey can do absolutely nothing to you due to Magic Guard while you can 2HKO with +6 Psychic (50.6% - 59.7%). Shadow Ball should be the primary option in the fourth slot (to hit other Rankurusu, Latios, Latias, etc.) followed by Hidden Power Fighting and Focus Blast. This set should also be the first one in the analysis.
This is a great post and you really should take it into consideration and make a mention in your OP of what stellar outlined in his post. Anyway, I love using this guy on PO with Trick Room in play, since it can be very deadly under the right conditions (I'd even go as far to say that it's better than CM). I couldn't find anymore problems, so I'll approve this once these changes are amended.