Ravenous Frenzy buff duration and stack tracker with an idle timer progress bar that shows when the spell will backfire if you remain inactive.
This ability does not give you a way to track what it considers "idle time," but with this weakaura I've managed to track it quite accurately, within 100 milliseconds from my testing.
The idle timer includes an extensive debug mode that can be enabled from the custom options tab. This debug mode will allow you to test how accurate the timer's estimation is for you. To test: Enable debug mode, use Ravenous Frenzy, and let the timer run out after casting a spell. There are several different events you should test: Casting a non-GCD spell, Casting an instant cast GCD spell, Completely casting a spell with a cast time, Interrupting a cast-time spell partway through.
Currently, Tranquility does not properly update the idle timer. I will update this once I find an optimal solution.
To load when testing Venthyr abilities prior to covenant choice, uncheck "Spell Known" in the Load tab.
Although beta build 36165 updated the idle duration shown on the tooltip from 1.5 to 2 seconds, the idle duration was not actually changed at all and this weakaura works exactly the same. ¯\_(ツ)_/¯