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.
Zeb what's your opinion on defensive Arbok. I'm going to write jc104's NU analysis and there are some posts I'm unsure of at the end. Well, just wanting QC approval etc. It's on the last page so it's easy to find :P