Best tank, healer and dps in mythic plus in Shadowlands

Best Tanks (ranking)

Vengeance Demon Hunter		Very high dmg dealer Very high self-sustain Very good mobility Defensive mitigation must be timed well. Has 3 types of builts to go more offensive or defensive: Kyrian Sigil Build Spirit Bomb Build Fiery Brand Build
Protection Paladin		Very high dmg dealer Overall good defense against several enemies, spell dmg, heavy dmg and physical dmg. Party buffs and survival. Good Self-sustain
Brewmaster Monk		Celestial Brew got nerfed and must be timed perfect. Dependent on healer (low self-sustain) Good utilities Very good mobility
Blood Death Knight		Strong utilities Battle Rez Immunities Good defense against several enemies Good defense against spell dmg High self-sustain
Guardian Druid		Very low dmg dealer Bad Self-sustain The Thrash legendary (Ursoc´s) got nerfed.
Protection Warrior		Coming to shadowlands with no "BFA borrowed powers" nerfed it drastically.

When it comes to dps, you have to take several other aspects in to consideration except for the dps.

These are the utilities.

What can you class contribute with except for dmg.

Purge

Priest

Shaman

Demon Hunter

Mage

Warlock

Hunter

Knockbacks

Druid

Monk

Holy/Discipline

Fire

Marksmanship

Elemental

Regarding dmg. There are different types of dmg. Here is a list of the best classes for each type of dmg.

Type of Dmg	Class (Spec)
AoE	Death Knight, Demon Hunter (Havoc)
Burst	Mage (Arcane), Paladin (Retribution)
Cleave	Mage (Frost), Priest (Shadow), Shaman (Elemental), Warlock (Affliction / Destruction)
Execute	Hunter (Marksman), Warrior
Single target	Rogue (Assassination)
Sustained	Druid (Feral), Hunter (Beast Mastery)

Death Knight (Blood) or Brewmaster Monk
Best Covenant: Night Fae for DK and Night Fae/Necrolord for Bewmaster.

Druid (Restoration) or Discipline Priest
Best Covenant: Night Fae/Necrolord for druid and Necrolord/Kyrian for Disc priest.

Rogue (Sub) or Demon Hunter
Best Covenant: Necrolord for Rogue and Venthyr for Demon Hunter
Mage (Frost)
Covenant: Kyrian or Night Fae
Warlock (Affliction)
Best Covenant: Venthyr