1. The size of the group, not the amount of real players in it is relevant, this is especially important for missions that require you to bring a hero (Nightfall).
2. Times for missions are determined in two different categories:
- 1st category: Missions that include a timer
(Prophecies: none; Factions: Minister Chos Estate, Vizunah Square, Nahpui Quarter, Tahnnakai Temple, Arborstone, Boreas Seabed, Sunjiang District, Unwaking Waters, Raisu Palace, Imperial Sanctum; Nightfall: Grand Court of Sebelkeh, Ruins of Morah, Abaddons Gate; EotN: none)
The time in these missions is determined by the time given to you at the end of the mission by the game itself – therefore, records for these missions are measured in seconds, not in full minutes. A single screenshot of a completion time is not sufficient, since the game does not state which mission was completed. It must be clearly visible in the video. - 2nd category: Missions that do not include a timer
(every mission except the ones listed above)
The time in those missions is determined by the time the mission-ending-cutscene starts, so you have to use some sort of SC-timer. Records are measured in full minutes.
Good luck and have fun!