WOW WIKI know about it.: Holy Knights : Paladin p2

A paladin that has chosen to spec retribution is able to increase his DPS by a considerable margin and fight several targets at a time with a good efficiency. Retribution damage favors slow two handed weapons and cause sudden damage spikes through both melee and spell crits. Through the now baseline retribution talent Crusader Strike and tier 3 talent Divine Storm they can deal considerable weapon based burst damage for AoE damage or for single target damage Templar's Verdict is a new melee range attack that deals additional weapon damage base on Holy Power consumption. Additionally, retribution paladins bring a large amount of raid utility, making them valuable in endgame instances. Retribution paladins are popular for their increased damage abilities for groups, such as Heart of the Crusader, which grants all attacks against the target a 3% increased chance to crit, and Communion, increasing the damage of the paladin's group by 3%.
Paladins are also excellent tanks. Spiritual Attunement provides the paladin with a percentage of mana,
based on ability level, each time they receive healing. They also excel at tanking multiple mobs at the same time through use of their reactive threat abilities like Holy Shield and Consecration, an AOE effect that deals significant threat to all mobs within range. Paladin tanks have gained widespread acceptance in the community.

The paladin class has some of the most mana-efficient and low-threat healing spells in the game, allowing them to easily fill the position of a main tank healer in a party or raid situation. Their healing efficiency makes them great endurance and battle healers, though paladins lack area of effect healing abilities (healing multiple targets at once) and healing over time effects. Paladins do have a form of indirect healing from the spell Judgement of Light.

Paladins have several anti-undead and demon abilities such as Exorcism, Holy Wrath, and Turn Evil which make them very effective when fighting Demon and Undead targets (not including Forsaken players, who are considered Humanoids for balance reasons).

In PvP, the paladin's most well-known strength is his / her ability to outlast his opponent (s). With plate armor, their ability to heal themselves and allies, and a near-complete invulnerability every few minutes, they are a hard target to take down. Paladins can also do a surprising amount of burst-damage and have good access to stun abilities. Paladins also make great supporting characters, buffing and healing team-mates while being able to survive the enemy's attention. Paladins are particularly vulnerable to Silence and Interrupt effects, as all of a paladin's abilities are part of a single magic school (holy). In addition,
dispel effects are powerful against paladins.

While Paladins have strong advantages (some players have cuttingly referred to them as 'Easy Mode') they are also an arduous excercise in multi-tasking. Thanks to their hybrid roles, inexperienced players may find them hard to balance as a whole. Any attempt to multi-task usually results in a much weaker character. There is also the issue of a Paladin's spell-casting abilities. While Mana will always be less important than to a mage or priest, it still powers the Paladin's most commonly used abilities, and must be juggled with Strength and / or Stamina.

Also, there are less paladin trainers than other standard classes (although druids also suffer from few trainers), and most of them are in the capital cities.