At this point in the game you probably already know about the last power to be unlocked at the Vindicar, the Fel Heart of Argus. Basically, this power keeps you from being killed when you take a lethal blow, stunning everyone around you for 5 seconds. This effect can only occur once every 30 minutes. It also regenerates your HP out of combat, if it's not on cooldown.
Knowing if a player has this buff or now may be vital for a successful attack, as you may not want to burn all your cooldowns on the first burst, since the enemy won't die quickly.
Taking that in consideration, I've created the the WeakAura below to show you, up front, if the enemy is under effect of the buff. It puts a big green heart on the screen when you target someone with the buff. If the heart is there, the target won't die in the first try. You are free to move the aura to wherever you want, but i suggest putting it like the image above, right behind the nameplate.
Attention: This aura is set up for the game in english and portuguese. You may want to delete the spell name in portugues, if you want.
Código da WeakAura