Guild Wars description
Smiting Prayers are useful for monks who want to deal damage. This is a very powerful attribute for many reasons such as that holy damage deals double damage to the undead and monk skills that deal holy damage ignore the target's armor, damage reductions, and other modifiers that affect physical or elemental damage. Another benefit is typecasting — other players will usually assume that any Monks they meet are healer monks, and therefore helpless. These players will be in for a nasty surprise as their seemingly helpless target fights back. However, this also works the other way - most parties will expect a monk to be either healer or protector, and it can be very hard for a monk with a smiting setup to get a group.
Aside from the simple surprise factor, Smiting Prayers deal a good amount of direct damage. Banish, Bane Signet, Holy Strike, Signet of Judgment, and Smite all deal direct, holy damage. Meanwhile, the skills Ray of Judgment, Balthazar's Aura and Symbol of Wrath deal holy damage per second. The skills Holy Wrath and Retribution both return a percentage of damage taken back to the attacker.
In addition to this large number of damaging skills, Smiting Prayers is linked to many more interesting skills. Many of these are geared towards making allies more effective in melee, like Balthazar's Spirit, Judge's Insight, and Strength of Honor. Scourge Healing helps take down healers, while Scourge Sacrifice will take down Necromancers with health sacrificing skills quickly.
Not entirely surprisingly, Smiting Prayers skills work quite well in combination with Healing Prayers and Protection Prayers skills. Zealot's Fire deals damage whenever you use a skill on an ally, while Smite Hex and Smite Condition provide a nice way of ridding teammates of hexes and conditions. Perhaps the best usage of Smiting Prayers for a healer is to simply dissuade your foes from fighting you by showing them you have teeth after all. Taking a large amount of damage they cannot prevent, while Scourge Healing works its magic, is a great persuasion method for those annoying Warriors who harass any healer.
Unfortunately, while many Healing and Protection skills use only 5 energy and gain a benefit from Divine Favor, Smiting Prayers skills tend to be much more expensive overall, and while Divine Favor allows the savvy Monk to reduce the number of times he or she has to use a healing or protection skill every battle, Smiting Prayers usually affect enemies more than allies, thus reducing Divine Favor's effectiveness, unless Smiter's Boon is used. As a result, because a Monk's energy supply comes primarily through conservation and amplified effectiveness rather than through reduced costs (as a Ranger), a larger pool (as an Elementalist), or energy recovery (as a Mesmer or Necromancer), the careless Monk who is used to only Healing and Protection will find himself or herself utterly without energy shortly into a barrage of Smiting. As a result, it is often a good idea to use Smiting Prayers more often on a caster with a Monk secondary than on a primary Monk. Of course, Primary monks certainly are able to be very effective indeed with Smiting Prayers, but they are at a disadvantage for energy management unless they make use of other energy management skills, such as a Mo/Me investing in Inspiration Magic, or just bringing at least one signet -- smiting offers the largest selection of offensive signets that inflict direct damage. This can also make a smiter monk quite difficult to disable; if they have Backfire or Dazed on them, or otherwise prevented from using spells, they can instead use their signets, and vice-versa with Rust.