I saw this question was originally answered on Reddit, but obviously that’s now private + I would like to minimise my engagement with Reddit if possible.
Basically: how does the Mythic World First work? Is it based on amount of successful raids? Is it based on time? Basically, what are the rules, if someone could explain.
Actually “tier” is used literally here as a level or grade within a hierarchy. With new patches typically comes a new higher level raid or higher tier raid. The term “tier set” is derived from that, as it is a collection of gear from a specific tier that provides a bonus when equipped together, not vice versa.
There are plenty of other sets of varying size that provide bonuses, most commonly known ones are pvp sets. But, tier sets are specifically sets that come from a specific raid release.