its because healing doesnt exist in a vaccume, all roles and classes play off each other. each dps has one mitigation (some get to be special and have two) and tanks by nature are also catogorized as support.
surrrrrreee midas and gordias could have been more instresting for healers , but they were such nightmare fights that again, nearly killed the scene entirely, shit , /i/ quit back then.
also nisi does punish yhe group if you mess it up, hence why i used it as a repsonse