You either give Healers the option to priority Q their DPS offspecs or alts after 3-4 rounds played as Healer, or you will have the long queues. There isn’t a second option to reduce the Q times.
I wouldn’t even be playing Dragonflight if I didn’t reroll Healer. I’m amazed people are sitting 30m+ DPS queues instead of playing other games or doing other things.