Is your feature request related to a problem?

The Dungeon 2.0 questline ends with a boss battle in Upper Blackrock Spire in The Beast's room. The boss you encounter is Lord Valthalak. This boss casts a devastating spell called Shadow Wrath. It is reportedly interruptible but I've yet to observe this. Whenever I've fought him, no cast bars display for Valthalaks himself, however his adds (Phantom Assasins?) correctly display their channel cast bar for Defile.
Describe the solution or feature you'd like:
Is it possible to detect and display Lord Valthalak's casts? Specifically for the Shadow Wrath spell? It would be helpful by giving warning to healers prior to the cast as well as function as an additional visual cue for the melee classes to use their interrupt.

Do you happen to know the approximate cast time for the ability? Wowhead just says its an instant cast time. (Normally cast times are either 0.5s, 1.0s, 1.5s, 2.0s etc)

Is this for normal Classic era or Classic Season of Mastery beta? Not sure if there's any difference in boss abilities from these versions.

I see what you mean on the wowhead page for Shadow Wrath. The comments on the Lord V page mention in numerous places the importance of interrupting the spell. Perhaps it is now an instant ability and only earlier iterations of the fight had a window of opportunity for interrupting the cast. In any case, thank you for your response!

Could also be a special channeled cast come to think of it. Sometimes they display 0 sec cast time if they have several effects attached to it.

I'll add it to next version just incase. Although the cast bar will probably restart every time Shadow Wrath ticks instead of showing a true channeled cast bar, but atleast this will make interrupting easier i guess.

thanks again!