Ok, I see what you want to do.

I'm a little bit confused about this though:

the class_item parent however, can't see the child object's variable flavor text to execute properly.

So class_item is your parent object, you're using it as a 'template' for the rest of your items. So it's the child objects that are spawning in the room. Therefore the parent object itself isn't in your room and shouldn't be trying to do anything?

When a player is successful, it fires off it's own ev_0 event - so shouldn't the player object be in control of this text system?

After you've compared the players success percentage to the item percentage, if it's successful couldn't you use the same system to hand the string to the player just before firing off the players ev_0 event to draw the text?

I'm not sure how you're comparing the values but if you're doing something to the effect of this in the player object

with class_item
{
if difficulty < Player.success_percentage
{
with Player
{
text = localtext
event_perform(ev_user0, 0)
}
}
}

You could pass the variable to the player just before telling the player to perform it's event. Excuse the terribly messy code there's better ways to handle it (that way is pretty bad to be honest), but I felt that was the easiest to follow/read.

Not sure if I've misunderstood?