Threat Management (Agro 101)

[Kothnok]

Hello everyone!  Welcome to this edition of Koth doesn't need to work, but can't play WoW yet.

I'd like to share my observations and experiences in general about artificially intelligent mobs and how they decide "what do I do next?" in combat.  All computer controlled entities need some way to decide who to attack, how to attack, whether or not to heal, run, or use some special ability.  Some systems can even learn and adapt it's strategies against their opponents (using neural networks or some other fancy thing).  While there is no published information on how mobs react in Worlds of Warcraft, coupling observations with a bit of reasoning we can come to a reasonable approximation of what to expect.

First, a few vocabulary terms just to be clear:
NPC: Non-Player Character is a role playing term to describe any non-hostile person/monster that is not controlled by any of the players. If movies were role playing games, the hero would be a Player Character (PC) and all the good guys would be NPCs.
Mob: Short for "Mobile Object", this term came about by programmers refering to all the different NPC's, beasts, humanoid enemies and monsters that roam about (or merely stand around) seperated from the landscape terrain and are typically able to be killed.
Threat/Agro: Threat and Agro are synonyms and both are a means to describe how important a target you are towards a Mob.

The basic ingredients to Threat involve Damage Dealt, Range of Target, Damage Healed, Spell/Item Threat Modifiers, Mob Abiliies Available, and a bit of randomness. =)

Lets take your typical Warrior Mob.  Their abilities available would be just "melee attack".  If PC_Warrior and PC_Mage both start to melee Warrior_Mob at the same time, then we have

	Dmg Dealt	Range	Dmg Healed	Threat Mod	Total	Threat Rating
PC_Warrior	50	Short (x2)	0	0	100	1st
PC_Mage	24	Short (x2)	0	0	48	2nd

As you can see, if we remove randomness from the Threat calculator, the Warrior Mob would determine that the PC_Warrior is the biggest threat and therefore would use the only ability it has and melee attack the PC_Warrior.

The Dmg Dealt is typically not "per swing" but "over the last x seconds".  Lets say the PC_Warrior continues to melee attack and the PC_Mage decides to instead cast a Fireball at our Warrior Mob.  Let's look at the effect that has on two different ranges.

	Dmg Dealt	Range	Dmg Healed	Threat Mod	Total	Threat Rating
While in melee range
PC_Mage	340	Short (x2)	0	0	680	1st
PC_Warrior	180	Short (x2)	0	0	360	2nd
While at long range
PC_Warrior	180	Short (x2)	0	0	360	1st
PC_Mage	340	Long (x1)	0	0	340	2nd

As you can see, PC_Mage stands a much better chance to avoid "gaining agro" by staying at long range in order to cast a damaging fireball.

Now lets give our Warrior Mob the ability to Charge.  Because he now has the ability to quickly get to a long range target, the range modifier alters slightly to reflect this new ability.

	Dmg Dealt	Range	Dmg Healed	Threat Mod	Total	Threat Rating
PC_Mage	340	Long (x1)	0	0	340	1st
PC_Warrior	180	Short (x1.7)	0	0	306	2nd

In this case, our PC_Mage will find himself being Charged by the Warrior Mob and get smacked for at least one attack.  This is the kind of behavior you will find in Strat Live with those Scarlet Warriors that charge around seemingly at random.

There are many spells that have threat modifiers as well as effects that can quickly reduce threat.  Druids only have a threat reducer while in cat form so they will find it harder to "dump agro" once it's gained.  Doing nothing while others attack the mob will reduce your threat rating, but that means you're doing nothing. =)  Aside from spells/abilities that specifically reduce your threat, there's some spells that will do so as a side effect.  Take the mage's ability to turn into a block of ice (or a priest's shield) for example.  After our PC_Mage is charged by the Warrior Mob, PC_Mage casts the Block Of Ice and becomes immune to damage.  Any time you absorb or become immune to damage, you instantly become less of a threat because there's nothing the Warrior Mob can do to damage you and it's a better idea to attack something it can damage.

	Dmg Dealt	Range	Dmg Healed	Threat Mod	Total	Threat Rating
PC_Warrior	180	Short (x1.7)	0	0	306	1st
PC_Mage	340	Long (x1)	0	Block of Ice (0.5)	170	2nd

An important thing to remember is that the amount of damage you do to a mob is not kept as a running total for threat as it only considers damage over the last several seconds.  Because of this built in timer, it is possible to do massive amounts of damage, wait a bit, then do massive damage again without gaining agro.  "Over agro'ing" is when a caster blasts the mob as fast as possible generating insane amounts of threat.  Generally, it's better to moderate how quickly you blast a target so as to avoid gaining agro and either dying quick or overly taxing any healers around.  Same thing goes for other classes that deal massive amounts of damage quickly.  I've found that for a druid in cat form, hitting the Cower ability every time it's cooldown is up while attacking generally keeps your threat from climbing too high.  I'm sure the same goes for rogues and their threat-reducers. 

Note that if you change the PC_Mage for a PC_Priest casting a bunch of healing spells, the same logic applies.  Heal too much too quickly and you'll find yourself facing a beating.  Luckily, priests have quite a few abilities to dump agro so that even if it happens frequently, they are generally able to reduce their threat pretty quickly.

I could go on with more complex examples, but I think this is plenty for now. =)

[Shadowwolf]

I actually use a Mod to tell me threat, however it doesnt work all too well for accuracy of anyone other then myself since no one else has it installed.

http://www.curse-gaming.com/en/wow/addons-3488-1-klhthreatmeter.html

Its called KLHThreatMeter and does a good job of listing in order of most threat the persons in the raid (provided everyone in the raid is using it). I picked it up on the few times I was on some PUG runs with the raid guilds as I saw what they were doing and wondered what it was for.

[un4]

I notice that there were no rogues in the examples