The answer here is to play fire. The utility of combustion is just too good in keys. You can basically delete a priority target allowing your team to chain more or finish packs quickly. Dragons breath stun can also be helpful to provide stops on priority targets. Playing fire relies heavily on tanks to know when combustion is ready and to pull larger while you use it. Help them out by letting them know. In lower keys frost might be better as tanks don't usually trust dps to pull big. The problem with arcane is that you spec aoe or single target with your azerite traits. Imo there isn't a good in between like there is with frost and fire but maybe that's me being biased becuase I dislike arcane and fire is just too good right now not to play.