Why do most of the players make a Priest as their favorite in the World of Warcraft? Are they a very strong class and help groups in ways that other classes can not? There are several reasons to make mention of it. Let us touch upon them one by one.
   First and foremost, Priests are very strong healer. They are capable of casting protective shields, heals over time, using group heals and many other types of heals that make them far superior to the other healing classes.
   Likewise they have great survivability. Priests are incredibly difficult to take down when they specialized as Discipline. They can mitigate lots of damage for being a cloth wearing and can keep a lot of heals on themselves without actually having to channel heals.
   Only does the Priest class receive these special abilities on the base of their race. Each race is granted a special ability at level 10 and level 20. These abilities range from dealing damage, special self-only buffs, or various utility spells.
Priests have two versatile ways of specializing. Either they have the ability to specialize to be Holy/Discipline or Shadow. Holy/Discipline is for Priests who want to heal. Shadow is for Priests who want to deal damage.
Priests can be a good caster DPS. If specialized as Shadow, a Priest can deal lots of damage, but more importantly give back health and mana to their group at a steady rate. This is a great perk for being a Shadow Priest and this is why there is such high demand for Shadow Priests on raids.
As one of the few classes, Priests are able to resurrect the dead. Inevitably, players will die in World of Warcraft. A Priest is one of a few classes able to resurrect these fallen players to return them to life. This is useful in almost every aspect of the game.
As above, they become more rewarding as you level as they are one of the few classes. At low levels, Priests are rather weak and may find it hard to solo. However, the higher a Priest's level, the better they are at being able to heal, deal damage, and solo. At the max level, Shadow Priests are one of the best classes to solo as and Discipline Priests are virtually un-killable.
Priests are able to reach the armor class of leather and mail users. With Inner Fire, especially if a Priest has the talents, a Priest will have more armor class than a leather user and just shy of a well-geared mail user. This is very useful when fighting against physical damage dealers.
Priests are regarded as one of the main buffing classes. The main buffs for them are Fortitude and Divine Spirit. Fortitude grants players with hundreds of health and Divine Spirit gives players an increased health and mana regeneration as well as increasing spell damage for casters.
Priests have great utility on raids and in groups. Whatever specialization a Priest may be, they bring lots of utility with them. They are incredible healers, great damage dealers with an addition of abilities that restore health and mana to their group, and are able to resurrect fallen players.
Those reasons talk about why most of the players make a Priest as their favorite. So we hope you can enjoy it.