[Warlock] Update HoG travel time and Wild Imp spawn timing

[millanzarreta]

The event timing chain for Hand of Gul'dan, Ruination, and Wild Imp spawns has been analyzed in detail using logs.

Hand of Gul'dan cast is a spell (105174) that uses a travel_time of 1_ms in SimC to mimic in-game ordering of cast-consumed effects. The spell data lists 700_ms, but that value is not used in-game. This then triggers the AoE Hand of Gul'dan Meteor (86040), a separate spell which starts the Wild Imp summon chain in its execute(). After its ~8ms travel_time (spell data lists 0_ms, but logs show a clear small delay), the meteor impact deals damage to the targets. The sequential Wild Imp spawn chain has a 1-2ms delay between spawns, including the first one.

The sequence of events for HoG would be as follows:

HoG Cast execute()
→ +1 ms (HoG Cast travel_time)
→ HoG Cast impact()
→ HoG Meteor execute()
  │
  ├─ Wild Imp spawn branch:
  │   → ~1-2 ms → WI 1 spawn
  │   → ~1-2 ms → WI 2 spawn
  │   → ~1-2 ms → WI 3 spawn
  │
  └─ HoG Meteor damage branch:
      → +~8 ms (HoG Meteor travel_time)
      → HoG Meteor impact() → HoG Meteor damage

Ruination initially works in a similar way. The cast (434635) has around 1000_ms of travel_time, matching spell data. It then triggers the AoE Ruination Meteor (434636), which is instant (travel_time=0_ms, as indicated by spell data). After the impact, Ruination for Demonology does not appear to summon Wild Imps directly. Instead, it triggers a HoG Meteor, which deals damage and summons the wild imps. This HoG Meteor trigger from Ruination has a delay of around ~395ms, with some variance that can be modeled fairly closely using a normal distribution.

The sequence of events for Ruination would be as follows:

Ruination Cast execute()
→ +~1000 ms (Ruination Cast travel_time)
→ Ruination Cast impact()
→ Ruination Meteor execute()
→ Ruination Meteor impact() → Ruination damage
  → ~395ms delay
  → HoG-like meteor execute
      │
      ├─ Wild Imp spawn branch:
      │   → ~1-2 ms → WI 1 spawn
      │   → ~1-2 ms → WI 2 spawn
      │   → ~1-2 ms → WI 3 spawn
      │
      └─ HoG Meteor damage branch:
          → +~8 ms (HoG Meteor travel_time)
          → HoG Meteor impact() → HoG Meteor damage

As a side note, both in SimC and in-game, if an Implosion is spell-queued while finishing a Hand of Gul'dan cast (with a cast time longer than the minimum 0.75s gcd), the Wild Imps may spawn after the Implosion cast, meaning they would not be accounted for that Implosion. According to in-game logs, this happens around ~14% of the time (measured with ~50ms latency, so it may vary), resulting in an average of 2.58 Wild Imps spawned after HoG that would be included in the pool of the next queued Implosion, out of a maximum of 3. This is similar to the average value obtained in SimC in this same situation after this PR. In any case, for this reason, it is generally not recommended to cast Implosion immediately after a non-Demonic Art HoG unless there were already at least 6 Wild Imps active beforehand.

Logs:

• (1) https://www.warcraftlogs.com/reports/qQbh9KN8f2d6HJrA?fight=last&type=damage-done&source=1
• (2) https://www.warcraftlogs.com/reports/kVLHNG7vdbYQZn96?fight=last&type=damage-done&source=1
• (3) https://www.warcraftlogs.com/reports/1akn36YZybBvtXqp?fight=last&type=damage-done&source=1

A figure corresponding to the log (2), showing the time between the HoG and Implosion casts across 1426 cases (orange indicates cases where the Wild Imps from the last HoG were included in the next Implosion, while blue indicates cases where they were not):