DO NOT upgrade your belt to tier set

[Ronalio-stormreaver]

This is from the official post on the subject by Blizz just this last week

The Creation Catalyst is Coming the Week of April 12

Greetings! The Creation Catalyst will become available to players after scheduled maintenance the week of April 12. To access it, you will travel to the far south area of Zereth Mortis that is the Catalyst Gardens. The Creation Catalyst is on a floating island above the main pool area and can be reached via flying or using a small teleporter right below it. [image] At a base level, how it works is you input a piece of Season 3 gear and a corresponding tier s…

Note that the 2-piece and 4-piece set bonuses will only be on the helms, shoulders, chests, gloves, and legs.