I disagree.
A necro doesn't need sleep to win, at all. If they catch somebody unpoisoned/poison wearing off then they can go for that sleep and try and get a nice advantage. If not, they can still kill their foe. Same goes for Shaman with one of the effects of insomnia. Both of these classes can dispel magic too, poison being able to be dispelled and the most common form being low level.
A thief can steal a sack full of poisining items from their foe and stop them poisoning themself. They have a trap that allows them to remove the poisoning effect too. Again, the most common form of poison is low-level and falls pretty easily.
Ninjas, having a little more melee power, can use the poison to their advantage. Strangle isn't as essential to a ninja as blackjack is to a thief (not saying it's not important, but IMO blackjacking on a thief is more important) and besides, there are downsides to poisoning yourself.
Firstly, the obvious one, is no regeneration. This you notice a lot when running because your moves drop quickly and you can't regenerate them quickly.
Secondly, is the damage. Sure, it's minor, but it soon becomes a little more painful when you're fleeing with awful wounds and you're poisoned. Classes that can't cure poison can only vomit once per 24 hours, that's one cure of poison per 24 hours, provided they've eaten recently.
Thieves, ninjas, necros and shaman have no problem in their ability to perform with things as they currently are provided they have a little smarts. Not to mention that there are a couple of other classes with the ability to do things that can be prevented with poison and without that, you can be considered as good as dead. Remove the ability for the rest of the playerbase to protect themselves from these skills and, well, I can't see it being a good thing...
Dey
