Hero behavior/Unexpected behavior

Before posting here: Please confirm potential issues on the talk page, so that we can provide accurate data. When identifying problems, please include the location where the problem occurred, the name of NPC using the skill, and the difficulty (hard mode or normal). See also: this post by developer Joe Kimmes.

This article is the counterpart of Hero behavior page. It gathers research made by users, basically stating how the hero AI activates skills different than a player would.

Questionable edits may be moved to the talk page for further debate.

Unused skills

These are those that AI never uses at all. A player will have to micromanage their skills monitor.

• Dark Aura: AI does not cast this on other party members who are sacrificing health and are under attack.
• Deadly Paradox: AI never uses this skill, even with Deadly Arts exclusive builds that do not have any dagger attack skills.
• Soothing Images: AI never use this skill; whereas monsters spam this skill upon adrenaline-using players.
• Test of Faith: AI never uses this skill, even when its the only adrenaline skill in a build, fully charged and ready for usage.

Limited-use skills

These are those skills that AI do not use to their full potential.

• Chaos Storm: AI casts only if foes are wielding spellcasting weapons.
• Mend Ailment: AI casts on allies but not on itself.
• "I Will Avenge You!": Hero uses when one corpse in earshot. Would be more effective if waited for higher number of deaths, e.g. if a pet has low hp and is likely to die soon, it would be better to wait.

Additional effects ignored

These are those skills that AI only use for their initial effect; but ignore subsequent and/or end effects.

• Fierce Blow: AI uses for the damage bonus, attacking targets without Weakness condition, wasting the chance to inflict Deep Wound.
• Heal as One: AI uses as a self heal; the life-stealing effect for the pet is ignored.

Inefficient skills

These are those skills that AI fails to time properly and/or use too often until they completely run out of energy.

Inappropriate spamming

AI spams them until their energy is completely depleted.

• Patient Spirit: AI casts it as a heal but the ally will still be targeted by another heal skill before Patient Spirit ends, which may cause over-healing (wasting energy and time). Although it is still worth the alternative in case target ally is being spiked. The problem doesn't fall on this skill by itself.
• Reversal of Fortune AI spams it until completely running out of energy. Should be programed to activate if target ally is below X % of health to give space for other prots.

Chaining

• Ritual Lord: AI doesn't use it immediately before activating binding rituals. Would behave better if the skill was changed to "You have +2...4...4 to all Ritualist attributes for your next ritualist skill." Skill really shouldn't be used for Signet of Creation/Binding Chains if spirits with long recharges like Shelter are on the bar.
• Signet of Illusions AI should prioritise use of non-Illusion Magic spells after this signet has been activated.

Failure to re-apply to maintain benefits

These are skills that a player would use before they end such that they gain the cumulative benefit.

• Aura of the Lich to maintain a higher Death Magic rank.
• Masochism misses the +2 Soul Reaping boost opportunity for the spell itself which lowers the sacrifice cost.

Wasted opportunities

• Berserker Stance: The AI wastes it by using a skill before building adrenaline.
• Energetic Was Lee Sa: AI drops the ashes immediately after acquiring them if their remaining energy is below 25%.
• Extinguish AI only uses it on allies within their aggro circle, even though the skill works within compass range.
• Overbearing Smash AI doesn't reserve it exclusively for KDed targets in order to inflict dazed.
• AI will use speed boost shouts: "Charge!", "Incoming!" and "Fall Back!" at once (ignoring effect stacking cap limit) even though it would be more efficient to use them sequentially.

Skills used for right purpose, but inefficiently

• Item spells can cause the AI to close-in to their targets at melee range, which can put mid and back-liners to dangerous situations.
• Signet of Binding: AI also steals ranger spirits, gaining limited benefit from such action as their effect is global.

Fatal damage negation skills

• Judge's Intervention: AI does not use on near-death allies, as they would use Divine Intervention. they frequently activate it outside of combat (like Death Nova) but rarely during combat.
• Watchful Intervention‎: AI wastes this skill on minions, should be saved for characters: party members, allies, NPCs that need survival e.g. mission npcs.

Misused skills

These are those skills that AI use without meeting requirements, wrong targets and/or unnecessary times.

• General: AI uses Bleeding, Disease or Poison skills on non-fleshy foes (e.g. Poison Arrow and Rotting Flesh).
  • AI uses condition skills on spirits which are immune to all except burning (e.g. Throw Dirt).

• Arcane Echo: AI ends it prematurely by following it with a non-spell skill.
• Lava Font: AI use this skill when foes enter earshot, even if no targets are adjacent to the hero.
• Signet of Creation: AI uses when there is a spirit within earshot, whether they control it or not. They will also not use it to take advantage of animated undead minions they control. Additionally, heroes use this skill after casting one spirit, even if they have more than one on their bar.
• Ward of Stability: AI also uses it versus enemies that do not cause knockdown, wasting energy and time. Shouldn't be used when it is not needed.
• Whirlwind AI runs in to use skill on foes in range, where it would be preferable for it to use it defensively when melee foes get nearby of their own accord.

Unexpected due to player's inexperience

These are skills which seem to malfunction by players with poor AI knowledge.

• Arcane Mimicry: Commonly seen with a UA partner. Some players will not want the AI to re-copy UA while the HB monk already is maintaining it, but the opposing alternative would require the player's micromanagement which would be much more tedious.

Verification requested

These skills were listed prior the last article overhaul without back-up support and need to be double-checked to confirm their statements:

• AI is unable to chain skills properly, e.g. glyphs with spells, forfeiting the combo's advantage (or at least not using it to its full potential). ^{[verification requested]}
• Spell Breaker when active on an ally, heroes will not cast any spells on the target including heals / prots and buffs.^{[verification requested]}

Notes

• Heroes and henchmen use the same AI (source), so this article also applies to henchman behavior (except for Modes and Forced skill use, which are not available to them).
• Heroes of the same profession use the same AI; they are interchangeable for all practical purposes. (See: the talk page.)

Trivia

• ArenaNet talk:AI bugs was the old wiki page to report AI bugs until September 2, 2009.

Historical Upgrades

• 2012, March 1st:
  • Reverted the last adjustment to the aggro range of heroes and henchmen.
  • Adjusted the speed with which Assassin heroes execute skill chains.

• 2012, February 16th:
  • The update changed skills that were listed in this same page under Missed-use and Unused-use sections by that time, the improvements had no specific details provided. (Talk:Hero_behavior/Unexpected_behavior_Archive_1#2.2F16_Update). This page has been overhauled ever since.
• 2012, January 5th:
  • Overhaul of the Elementalist profession led to unpredictable AI behavior.
  • Adjusted the AI’s usage of: Double Dragon, Gust, Mirror of Ice and Stone Sheath.
• 2009, June 18th: AI updates to Heroes and Hard Mode NPCs.
• 2008, August 7th: AI updates to Heroes and Hard Mode NPCs.
  • The AI does not always activate skill as they change; some skills are still used as their version prior the game update (e.g. Healing Burst as a Touch skill).
• 2007, August 31st: New heroes introduced via Eye of the North expansion.
• 2006, October 25th: Heroes introduced to Guild Wars via Nightfall campaign.