Figuring out when they are fired is easy. In fact every combat logger can do just that. It is just another damage event.
The thing is we have no idea what the cooldown is, so we had to guess when it expires. In particular we could not reliably adapt to the effects of the lower cooldown Trait/Hundings Rage set bonus wich lowers the cooldown.
Also note that there might be a slight bugg with dual wield:
If you have the same enchantment on both weapons, either weapon procing will start the cooldown for both enchantments.
Last I chcked, internal cooldowns for weapon enchantments were 4 seconds.
Couldn't you just manually start a counter every time the weapon enchant combat event happens and take into account whether the weapon has the Powered trait (50% at legendary) and whether or not the player has the Torug's Pact set?