An OO mention is probably the best bet, mentioning that as a defensive Poison-type it can absorb Toxic Spikes (which is its only real merit over Weezing, imo). There are just other, better Poison-types that can pull off a defensive-ish set, like Garbodor or Muk or Weezing. The additional Speed or power really doesn't mean too much when you aren't investing in either. Arbok's real niche is a pretty good Coil set and Shed Skin, so we should just keep it to that I think.