Assassin's Enchant Poison is still useful, even if you're already a GX. It gives a decent damage boost from monsters that are weak to poison*. And it gives you roughly 50% total damage boost when hitting a poison weak mob with a GX skill, Venom Impression at max level.
It also stacks with EDP and still gives you a good chunk of damage boost to those weak to Poison.
Heres a vid with Enchant Poison and Venom Impression against an MVP: http://www.youtube.c...h?v=Jmr-WorvZOc
Also, monsters that are poisoned (poison status effect) receives more damage from any attacks (maybe except Soul Destroyer, not sure) than when they are not poisoned. Not sure how much % of damage is that though.
Lastly, EDP requires a poison bottle, and Poisonous Weapon also requires a specific item, both skills require zenny to use. Enchant Poison requires 0 zenny to use, and you will need it as a prerequisite for a SinX skill, so you will be dumping at least 5 or 6 points into it. Requiring zenny meaning, you need to either buy them from vend since I doubt you will have fun creating those items instead since your build will be most likely not specified for creating them, specially for Poison Bottles.
Monsters that are weak to Poison* element: Earth, Wind, and Fire element monsters. Poison element deals about 25% more damage to those three elements.
The only time Enchant Poison will be "useless" is when you have a gazillion zenny to spend since you will most likely use an Elemental Katar or Elemental Converter for your elemental needs. For a player that is unfunded or just starting out from scratch, Enchant Poison is far from being useless.
Edited by Kandine, 19 March 2014 - 03:24 PM.