Guild Wars 2

While I lack the ability to cite any source by ANet on how aggro is gained, it is important to note that there is a distinction between damage dealt vs damage dealers in the party. Top damage dealers are not necessarily going to take aggro for dealing the most damage in the past; however, top damage dealers by nature, so long as they continue to attack, will deal the most damage per unit of time, which is confirmed as being part of how aggro is measured. If they stop, their priority is lowered, which is also often tied closely to proximity, as often people only stop attacking when out of range.

That said, I believe there has been substantial community testing/response on the matter, and that it has been relatively agreed upon that armor value is taken into account for considering aggro in most typical encounters. How those weights are valued, however, is a different story; some encounters may have a very low weight assigned to this, while others may have very high weights assigned (Mossman).

MadRabbit.3179:

DeceiverX.8361:

Yes, initial aggro is based on a combination of proximity, armor, and player-output damage as a means of splitting aggro. It’s why the taunt condition is frivolous (especially with break bars). I don’t recall a period where this wasn’t the case.

I ask and I leave it out, because the wiki for Aggro doesn’t include armor as part of the aggro calculation in the “Gaining and losing aggro” section.

https://wiki.guildwars2.com/wiki/Aggro

It addresses the armor issue with this statement

“Some players have suggested the following factors might influence certain enemies, but this is not confirmed by any official source (and seems to be based on assumptions from other MMOs that go against the principles stated by Guild Wars 2 developers):

1. Top damage dealers [citation needed]
2. Who is using a shield / has more toughness and overall armor [citation needed]"

I wasn’t sure if this was current or just misinformed due to a lack of citations in the article.

In my part, it’s based on experience and experimentations. Since ArenaNet neither confirm nor deny the effect of toughness or armor, it is still easy to verify once you run your own experiments. Thus, for those who runs dungeons and fractals, this is a common knowledge.

Here’s one example of experiment and fact finding — The Aggro Magnet Guardian

Important notes:
“…having more toughness will actually attract more aggro on lots of instances, especially bosses.”

“Once I get all that down, the plan to gain and maintain aggro is easy: In order of importance
1) Stack toughness”

Also, there’s an interview that semi-confirm the toughness aggo effect;
ARENANET’S STEVEN WALLER DISCUSSES GUILD WARS 2’S RAIDING FOUNDATION

Important note:

“…in the encounter you just took part in there is definitely the opportunity for someone to draw aggro on the boss, but it’s not tied to a specific profession. It’s instead tied to the amount of Toughness you have…”

However, the mobs in the open world have a different AI programming which doesn’t respond to your specific stats. It seems that the mobs in open world has certain agenda or preferred targets regardless of what other players are doing within the proximity. This you’ll notice that there are mobs who zeroes in on you and not stop until you go down even though you have not dealt damage to that mob and other players are actually killing it. Some other mobs just randomly switching target.

EDIT: Another source.

GW2 Vale Guardian Raid Boss Guide

Important note:

“You want to run as much Toughness as you can so your healer doesn’t pull aggro off you since aggro is Toughness based.”

There are bosses that focus the ones attacking them first – Tower Lords and some PvE champs/bosses.

Thanks, guys. All of that is really interesting. I’m genuinely curious here, because I don’t really know and I thought the wiki sounded a little out of date and unsure of itself.

I only have one character, my elementalist, that runs a gear setup with toughness, so I don’t have much experience with it’s influence on aggro.