I have little to no experience with Gen 5 so any input is helpful :D
http://veekun.com/dex/pokemon/drapion
[Overview]
<p>Although Drapion hasn't gained anything significant in Gen 5, it already posesses everything it needs to succeed in OU. It's one of only three phazing Toxic Spikers (the others being Nidoqueen and Nidoking), also being the fastest of the three with 95 base Speed, and the only one that can effectively wall Reuniclus. Its 110 base Defense provides good bulk, while its less-than-stellar Special Defense is covered by its Poison / Dark typing, which gives it an immunity to common Psychic attacks and a resistance to Ghost attacks, two largely special-attacking types. Drapion can also dent several Pokemon with its 90 base Attack and decent STAB moves. All in all, Drapion is an excellent niche Pokemon that shouldn't be underestimated.</p>
[SET]
name: Toxic Spikes
move 1: Toxic Spikes
move 2: Taunt / Whirlwind
move 3: Crunch
move 4: Earthquake
item: Leftovers
nature: Careful
evs: 252 HP / 4 Def / 252 SpD
[SET COMMENTS]
<p>This set is Drapion's best attempt at competing in the OU environment. Due to its bulk and Speed, it can easily set up two layers of Toxic Spikes and utilize Whirlwind to phaze the opponent. Taunt prevents other Pokemon such as Ferrothorn and Skarmory from setting up, and it also prevents Reuniclus from beating you one on one. Crunch gives Drapion a reliable STAB move for beating Ghost- and Psychic-types, and Earthquake is the best option to hit Steel- and Poison-types super effectively, two common enemies of Toxic Spikers.</p>
[ADDITIONAL COMMENTS]
<p>As for other options, Drapion can hold a Balloon to remove its only weakness, though it is lost after one hit. Alternatively, you can pair Drapion with a Flying-type such as Skarmory or a Pokemon with Levitate such as Bronzong. Knock Off can be used instead of Taunt or Whirlwind, which can be helpful when it comes to removing Choice items and Leftovers. Wish support is recommended when using Drapion as as it has no form of reliable recovery; Pokemon such as Vaporeon and Jirachi are great options due to their good defensive stats.</p>
<p>Partners who can take advantage of Toxic Spikes are helpful, especially those who have access to Substitute to stall the opponent and worsen poison damage. Pokemon such as SubCM Jirachi and Torment Heatran are great options due to their excellent typing and decent defensive stats. Another partner to consider is a Pokemon who can block Rapid Spin; Ghost-types such as Jellicent, Golurk, and Dusknoir are great options, and each of them have decent stats and unique support moves. This set also appreciates support from entry hazards as Drapion is such a good phazer, examples include Skarmory, Metagross, and Forretress.</p>
[Other Options]
<p>A Choice Band set could be used with its decent movepool, but Drapion will have trouble sweeping in the Gen 5 OU enviroment due to an array of faster, more deadly sweepers. Swords Dance is available, though Drapion is too vulnerable to faster Earthquakes and is generally outclassed. Pursuit can be used to hit Ghost- or Psychic-types as they switch out, and is a nice STAB move. Drapion also has access to the elemental fangs, they aren't the most powerful moves around, but they help provide type coverage. A gimmick set with Sniper, Scope Lens, and attacks with a high critical hit rate could be used for laughs. Acupressure can be used to raise Drapion's stats randomly, though this is very unreliable and will usually end in a disaster.</p>
[Checks & Counters]
<p>Taunters with Mischevious Heart such Whimsicott or Thunderus can prevent Drapion from using Toxic Spikes and Whirlwind, effectively crippling the set. Nidoking can absorb Toxic Spikes as well as hit Drapion with STAB Encourage-boosted Ground-type moves, though Drapion is faster and has access to Earthquake to hit Nidoking super effectively. Skarmory is not only immune to Toxic Spikes, even when grounded, but it is also immune to Earthquake and has access to Whirlwind to phaze Drapion. Breloom is also problematic; not only does it have Poison Heal, but Spore gives Breloom a much easier time setting up, though it will have hard time KOing Drapion. Forretress can remove entry hazards with Rapid Spin, while taking little damage from any of Drapion's attacks and having access to Earthquake to hit it super effectively.</p>
[Dream World]
<p>Drapion gains Keen Eye as its Dream World ability, though it's pretty useless because there are no common moves which lower accuracy.</p>