I had someone say this in a party recently, as well, but like the other posters, I have seen weakness triggered many, many,
many times while Paralyze was on.
However, I can understand why it
might create a problem.
Allow me to explain. When a player is casting a spell and that spell gets interrupted — whether through movement, paralysis, or stun — our "casting bar" continues to move forward, even though the spell is botched. This is important. If a player is paralyzed and they try to swing at a mob, the action is prevented by the paralysis: that action never happens. However, if they try to cast a spell, it will let them start the spell, only to be interrupted halfway through when the paralysis actually kicks in.
Imagine that monsters also have a "casting bar." When they're paralyzed, they still get to cast spells, but we're all hoping that the spell will get botched by the paralysis. But when it does, there's still a cooldown period after the paralysis message where the spell is still "being cast." That little window
might also prevent weakness from being triggered.
If that
is the case, then the solution here is simple: people triggering weakness need to pay just a little bit more attention, and if a spell gets paralyzed, give it a couple seconds after that to "complete casting" before trying to trigger weakness again. Which shouldn't be a problem, since they should have been holding off while it was casting
anyway.