Filling in the Fault Lines

The biggest threats to an OU Arbok are bulky Ground-types seeing as they resist Arbok's primary STAB-attack and can retaliate with a super-effective STAB-attack of their own. Celebi can be considered the best OU pairing with Arbok due to its access to Heal Bell (which removes a Resting Arbok's status) as well as its resistance to Ground-type attacks and the immediate threat it poses to Hippowdon and Gliscor with its STAB Leaf Storm. Gliscor, however, can strike Celebi with a 4x super-effective U-turn, which is where Suicune can potentially come in. Due to Suicune's high defense stat, it can be teamed up with a specially defensive Celebi and OU Arbok to provide adequate coverage and support to aid in Arbok's sweep. Rotom-H, however, can provide the same support as Suicune due to its spectacular defensive stats and its resistance to U-turn, but it lacks the ability to hit Gliscor super-effectively and also leaves a vast opening for Tyranitar to switch-in a sweep your defensive core. CB Scizor can alleviate this Tyranitar threat with its extremely powerful STAB super-effective priority with Bullet Punch, but one must always be careful of the occasional DD BabiriTar with Fire Punch.

Heatran can OHKO Arbok with Stealth Rock residuals and one turn of Life Orb damage, so a reliable counter to this Pokemon is useful for Arbok's sweep as well. Suicune is a great counter to Heatran, but perhaps, in this case, Vaporeon would be the better choice due to Arbok's defensive nature and Vaporeon's specially defensive nature, access to its oft-unused Heal Bell, and always useful Wish support.

In the end, a strong core of Celebi, Scizor, and Vaporeon/Suicune (depending on your Celebi's EVs) will provide your OU Arbok with the proper support it needs to stick around throughout the course of the battle and to repeatedly strike the opponent with its ridiculously powerful STAB attack.