I'm not sure if this has been discussed previously or not, I wasn't able to find a thread to add to. Currently the only way you can tell how many charges your weapon has left is by executing a single click on the poisoned weapon. This becomes a pain in the butt during PvP. Currently not every weapon strike will successfully land a poison, this adds to the difficulty in keeping track of poison charges. Sometimes I find myself wasting a poison application to my weapon when I see several swings without poisoning my opponent, when I actually still have several charges left. TL;DR : I propose a system message when your weapon runs out of charges.
I like this idea. Plus, as far as I can tell the charge count no longer shows on the weapon whatsoever. When I single click a poisoned weapon I see the weapon name/specs followed by "it appears to be poisoned."
If you have the skill to determine how poisoned (ie: Poisoning skill), you will see the appropriate message.