If I remember correctly, the stated inspiration for Legendaries in Legion was the random epics that used to drop in Vanilla WoW. Things like
Freezing Band.
They wanted to capture the excitement of finding a unique item with a unique effect, as well as the "I can build my character around this"-RPG feeling that they gave.
If that's what they were going for, then they obviously missed the mark with Legion's Legendaries. People view them as mandatory power increases, and the pure RNG system makes the entire thing frustrating and leaves players feeling like victims of the system.
I would have preferred if they went with a system like this:
- The bonuses are largely situational / non-throughput, but still potentially combat useful. The majority are still class-specific.
- The item level is slightly higher than a Heroic Raid. That means that players are still excited when they loot them, but their power level isn't so crazy high that they feel mandatory just for the stats. High-end players aren't obligated to grind for them. Equipping them to leverage their unique effects for specific encounters becomes a choice instead of something that's mandated.
- Legandaries are now Epics with a special tag of some sort (so that Legendary items still feel special in the future. Making something Legendary used to really mean something.).
From the very moment they announced them, I thought that the Legendary system seemed risky. Artifacts always looked awesome, but Legendaries looked like they would either be (at best) unobtrusive and (at worst) a frustrating imbalanced RNG slog. The result is somewhere in the middle. The expansion would have been fine without it, so I'm still somewhat baffled as to why they felt the need to make them such a significant part of character progression.