A hybrid takes up the roles as a tank, healer or damage dealer. The class can be considered hybrid because of it has several different group roles, which depend on what talents the character has and the type of equipment it has. With all three group roles, many players are expected to know how to play their class. If you do not have the talents or gear, it does not matter. To play a hybrid, it takes a dedicated person who is willing to learn the finer aspects of their class and be open to change.
   There are three classes like Druids, Shamans and Paladins, cam be more than one of the role above. These three classes are considered the truest hybrids, as each of them can cover the three roles of tanking, damage, and healing.
When it comes to Druids, they are a hybrid of tank, healer, and melee, ranged damage dealer, depending on their spec and gear. Druids have average to excellent healing ability, for example, Feral Druids inherently have an expanded mana pool but no mana regeneration enhancements and Balance Druids have an expanded mana pool enhancement to both damage and healing, but less mana regeneration than a restoration Druid. Mark of the Wild is one of the more powerful buffs in the game, which offers a good general boost to most classes and specs. Shape-shift ability allows Druid to serve as a tank in their Bear or Dire Bear form and increases their survivability if drawing aggro by accident. They are all but immune to Polymorph and other Root or Snare effects as they can simply shape-shift to free themselves. Tree of Life Form likely has the most mana efficient heals and is specifically geared to raid healing. Tank abilities are viable for raids, optimal for single targets and less than optimal for a very large number of targets. When Druids reach their high level talents in each tree, they can provide a raid healing or DPS aura. Rebirth is the only resurrect which can be cast in combat.
   But their disadvantages are that they are lightly armored in caster gear, just a little tougher than a cloth wearer in humanoid form. However, Barkskin combined with Dire Bear Form or Moonkin Form provides enough damage mitigation and time for a main tank to re-acquire a mob. Rebirth is on a 20 minute timer once it has been used. Druids lack traditional CC, relying on Entangling Roots, a spell which only works in outdoor instances. Though effective, Hibernate is only castable on beasts and dragons. Cyclone serves as a temporary patch when another crowd control breaks.
   The Paladin is incorrectly thought of as a hybrid of Warrior and Priest. Paladin tanks rely on reactive Holy damage as the primary source of threat and on direct holy damage, functions by the seals.
   Paladins are armored in plate and take lots of damage, which are widely regarded as the single hardest class to kill. They can be a long-lasting and efficient single-target healer. Available to them is a wide variety of important buffs for all classes. They have several auras with various beneficial effects for the party. One of 3 classes is capable of allowing quick recovery from a wipe with their Divine Intervention. They can use Divine Protection and Divine Shield to protect themselves from incoming damage or cast Blessing of Protection to protect other players from physical damage.
   But Paladins have very little in the way of ranged attacks, which is why some of them take up the profession of engineering, giving them access to throwing weapons, like bombs. Paladins also have relatively sparse protection against casters.
The Shaman is a hybrid of healer, melee and ranged damage dealer, with limited tank ability and that is only dependent upon the player and gear.
   Shamans are versatile regardless of build, letting them switch from tank to healing mode or damage dealer during a battle without needing to change their talents. A wide variety of totems can be used to buff party members and debuff opponents ability to heal and resurrect makes them very useful to a party. They are only a class capable of solo-recovering a raid via Reincarnation, albeit only once per hour. Chain Heal is one of the best multi-target healing spells in the game.
   But Shamans can not tank past regular 5-man dungeons past level 60. Stationary totems can only affect party members, not a raid. The Shaman has no direct buff to offer other players. They are also not very mana efficient as non hybrids. Another area where they are lacking is they have no CC spell like Polymorph or Fear. If a Shaman does tank, they lack abilities can make it difficult for tank to regain aggro if Shaman angers other opponent.
   As above-mentioned, these three classes are regarded as Jack of All Trades at times, and can be rewarding if you can master each of their group roles and be able to switch when needed.