Can you provide some specific examples?

Hmmm, well posting all the relevant code would be a bit messy but in short I use some code with EVENT_EFFECT_CHANGED to link a target unit id to a group unit tag and then in EVENT_COMBAT_EVENT I pair it back and display certain alerts based on conditions. The other target parameters are indeed empty so I suppose from a developer perspective you might actually have intended to NOT allow such things. I understand that in pvp this kind of stuff might allow unfair foresight but I do not believe it hurts anybody in pve.

I've opened a dialogue with some of the game design teams about what we want to allow for combat addons like this. I'll post back when I hear something.

I used pretty much this in my PvpAlerts before Homestead changes:)

Currently i wasn't able to find a way to link anonymous events by targetUnitId to EVENT_EFFECT_CHANGED ids to any benefit, since, at least in pvp the code seems only to send the later about allies.

I'm curious what is left in pve, that you built an addon feature out of it?

After talking to the dungeon team they are willing to put in a buff for the light/dark state on the 2nd boss in Maw of Lorkahj which should allow tracking by addon. In the future we could open COMBAT_EVENT up a bit more but it would take a large audit of all the spells being cast by NPCs since there are a number that should not be known to a player client (this is also true of buffs and debuffs). This would be at a later date, but is something we want to clean up anyway.

Thanks for your amazing work, chip, that's really good news! As a "rule of thumb" I feel that every effect that has a duration and is communicated by changing the visual appearance of your character (glowing hands, heads, etc.) should be communicated via EVENT_EFFECT_CHANGED for the sake of visibility in large scale combat situations. If you could add the fields sourceName and sourceUnitId or at least combatUnitType to EVENT_EFFECT_CHANGED it would make it absolutely perfect :)

Just out of curiosity: What type of buffs/debuffs/combat vvents shall not be visible to the client and why?

sourceUnitType is already in EVENT_EFFECT_CHANGED.