Alcaras, the creator of Subcreation, pulled up some interesting data from the site’s archives and ranked all specializations based on their Mythic+ performance from Battle for Azeroth Season 2 up to Shadowlands Season 3.
The individual specs are ranked based on their Mythic+ performance by roles (e.g. tank, healer, melee DPS, ranged DPS). You can find the spreadsheet here.
Source: Reddit