How i can track my Holy Wrath stun (prot pally), on specific enemy if he's not my target?
With WeakAuras, i can't track specific enemy units... only friendly players. And multi-target track ALL stunning target.
I wish track my stun on Ball Lightning (lei-shen), but only the Ball Lightning. And say anything in the chat like: "Stunning ball done"; without spam (a lot targets).
Is hard to make it in custom trigger!? Anyone can recommend an addon where i can make it (easy and exactly this thing)?
It's not very straightforward to do with WeakAuras because of how the WoW API works. You can't just get information on a specific enemy unless it's tagged as a raid "boss", it's your focus or mouseover, or somebody in the raid is targeting it. Since in your case none of those are guaranteed, you'll have to do it a different way.
With a custom trigger you monitor COMBAT_LOG_EVENT_UNFILTERED for a SPELL_AURA_APPLIED for the correct aura where you are the source, and then I think you'll have to just assume that stuns aren't on DR and send the duration info as 3 seconds. You also use a local variable to not trigger any chat messages more than once per trigger.