Its much different from the fun we had boxing m+ in Legion.

Dungeon mechanics are brutal for multiboxers this expansion. Brutal on melee, brutal on non-mobile ranged, just brutal. The people boxing mythics such as SerKensington are using a traditional trinity setup. But he needs tons of VideoFX and custom setups to get through everything, its lots and lots of work. But if you want to go the furthest you need a trinity.

If you want an easier time and have fun, 5 hunters. You can live without a healer if you pick the survivability azerite traits instead of DPS. If you only want to do mythics then this is the team I would concentrate on.

If you want an all-around fun team, 5 Blood DK. Their DPS is too low to do really high mythics but their survivability is top notch allowing really big pulls. They are also God Mode in WPvP and World Quests. If you want to play the whole game then this is the team I would concentrate on.

I stopped at end of season 2, but I doubt much has changed since then. Good luck and have fun.