Terraining is at least at Blizzard campaigns level.
An alternative storyline that gives character arcs or at least some personality to all main heroes – but keep in mind Blizzard didn't do much with some of them like Vashj so your interpretation of them could be different from mine– it IS a fanfiction in campaign form after all.
Tons of custom resources mostly from this site for units, icons, spells, and doodads for better terraining + a few sounds for atmosphere : almost 500 files total.
All custom music : for cutscenes and gameplay, with different tracks for some maps (holdout missions for example) for better immersion : 36 tracks total.
Quality-of-life features : all cutscenes are skippable (duh), all units are paused when the camera shows you something, creeps buildings are either auto-attacked or non attackable, crates that can contain items are a different color than those that are just scenery, rocks chunks all die when you destroy one, etc.
No padding in the cleanup of enemy bases : you can destroy every enemy unit and building if that's what you like, but the objective is usually a particular building or at worst stopping the production capabilities of the enemies (there is one exception but it's not exactly a traditional base).
Rewarding exploration : side quests, creep camps and items to find + One special hidden Easter egg on each playable map.
→ from the ice of Northrend to the jungles and city of Theramore, but also the ruins of Lordaeron, mountains of Khaz Modan and desert of Barrens
Maps with different tilesets (and different weather conditions/atmosphere).
→ at least 1 new playable unit on each map, and most new units are introduced on a map where they are particularly useful (like in Starcraft 2 campaign)
Expanded tech-tree for each playable race + the dwarven race as an enemy.
→ for example : a holdout mission but it's a naval mission or a whole city, or a squad mission with a stealth phase + 3 maps have scripted boss battles Why would you want to play this campaign ?