Guide to playing as a Mesmer

Overview

Mesmers are usually considered the most difficult class in Guild Wars, but if played well they can cause a lot of trouble for the enemy.

Mesmers can neither heal nor cause flashy damage, their influence on the battle is subtle, which is one of the reasons why they are often underestimated. Although subtle, the mesmer is capable of turning the entire battle with a well placed spell. A mesmer can shut down a character on his own, interrupt his actions, remove the enemies' adrenaline and energy or cause degeneration. A mesmer can even use someone's own energy against them with skills like Energy Burn and Aneurysm.

Attributes

Fast Casting
The primary mesmer attribute, Fast Casting has the inherent effect to reduce the casting time of all your spells and signets. Most of the few skills in this attribute are also good at enabling a mesmer to cast spells more often, like Mantra of Recovery and Stolen Speed.

Domination Magic
Skills of this attribute excel at punishing the actions of your foe, through spells like Empathy, Backfire, Power Spike and Mind Wrack. This attribute is the mesmer's best direct damage source.

Illusion Magic
Skills of this attribute will usually be used to hinder enemies, through spells like Soothing Images, Arcane Conundrum and Sum of All Fears. It is also good at causing indirect damage through health degeneration, with spells like Conjure Phantasm and Images of Remorse.

Inspiration Magic
Skills of this attribute are usually related to Energy Management, both helping the Mesmer keep his energy on as well as taking off enemies's energy (through spells like Energy Tap and Ether Phantom). This attribute also contains the two only self-healing skills of the class: Ether Feast and Drain Enchantment.

Understanding the Profession

PvE
A mesmer has a bad position in PvE as groups rarely look for one. They neither fit in the Tank, Damage dealer nor Healer category so most people do not think of mesmers as a good addition to the party, you will most often just be accepted because the party has tanks, damage dealers and healers sorted out.

Most mesmer skills need some time to really influence a battle, making them useless in the fast paced PvE, your enemy will most likely be dead before these skills achieve their goal. This is why most mesmers focus on Domination which has some quite powerful damage skills, i.e. Energy Surge and Energy Burn. The damage from these skills is still tiny compared to the damage of Elementalists or Warriors. Domination mesmers can also stay in the back of the group and hit the tanks or dervishes with empathy in order to protect the monks and elementalists. Other Mesmers focus on their secondary class, taking advantage of the mesmers Fast Casting, using skills that normally take too long to cast, like Meteor Shower.

A powerful but even less visible style of play is the interruption mesmer, using skills to stop the enemy from using his spells. These mesmers usually concentrate on the enemy casters, interrupting healing spells or skills that could hurt the team. The weakness of this approach is that the only enemy casters likely to live long enough for interruption to be worthwhile - bosses - activate skills in half the normal time (except in the Prophecies campaign) making them difficult to interrupt.

Mesmers may also wish to play a mass degen build, using the skill Mantra of Persistence in conjunction with many of the Illusion Magic spells, mainly Conjure Nightmare, Conjure Phantasm and Images of Remorse. The main benefit of this kind of build is that it can cause severe damage to any kind of foe and mesmers can stay well back from the fray, as the degen hexes will last a very long time so the usually weak mesmer will stay alive much longer. Other skills can be used in conjunction with this kind of build such as Accumulated Pain to inflict a deep wound as the conditions for this spell will be easily met.

Naturally, any enemy or boss with hex removal spells, especially Convert Hexes or Withdraw Hexes will easily be able to counter this build, so make sure to research the kind of enemies you will be facing so as to see if this build will be of use.

Mesmers can run a conditional build if they wish by stacking skills such as Spiteful Spirit, Empathy and Backfire. These skills can cause major damage to any kind of enemy and are an effective way to deal with melee and Monk bosses, due to the regularity of their actions. This build is even more effective in hard mode due to the faster speed at which enemies attack and cast spells.

For most builds, Inspiration Magic is recommended for Energy management.

PvP
PvP is the area where mesmers show their full potential, shutting down the enemy backline singlehandedly, assisting spikes with the other hand by removing defensive enchantments with skills like Shatter Enchantment.

The first thing a mesmer should learn is to think like the enemy. Try to get a feeling for the enemy, when does he cast his spells, how much energy does he have and so on. A well timed Diversion disabling a Word of Healing might cause the enemy to retreat, panic or die.

The second thing a mesmer should learn is to find out what might annoy your team most, like "Do they have a Blinding Surge Elementalist preventing our Frontline to kill them?", "Is their Mesmer good enough to prevent our Monks from healing us?" or "We play a condition build, do they have a monk with Restore Condition?".

Make sure your team knows when you have disabled an enemy skill so they can take full advantage of it.

Also, mesmers should have a health regenerative skill handy like Shadow Refuge, Troll Unguent or Healing Breeze in order to cancel out degenerative Ranger attacks like Burning Arrow.

Staying alive
Because of the low Armour rating of mesmers, it is best to stay in the midline. Kiting is also an effective tactic.

What to Avoid
Damage: A mesmer should avoid any direct contact with the enemy. A combination of a maximum of 60 Armor and weak self-defense makes it is easy to get killed by even a single enemy.
It is easy for a mesmer to get killed easily in Factions and Nightfall due to the many missions. Be sure to pick a good secondary profession to help avoid taking Death Penalty.

Choice of Secondary Professions

Monk, Ritualist or Paragon is often used to provide a reusable Resurrection skill. This is especially useful as Fast Casting affects these slow skills, something known as a Rezmer.

Warrior class can be used mostly because of some defensive skills like Defensive Stance and Sprint. However, since most of the Warrior's skills are melee attacks, few of this class' skills are useful for a Mesmer.
Ranger has very little utility for for a Mesmer. However, Melandru's Resilience can be used for farming in condition/hex heavy areas, although this is not very common.
Monk is often used to even out the bad self defense of the mesmer. Often this includes a hard res that takes advantage of Fast casting.
Necromancer most often includes builds that make use of Fast Casting on slow Necromancer hexes. Some Necromancer hexes combine well with Mesmer hexes, like Reckless Haste and Spirit of Failure cast on one target.
Elementalist can be used for fast casting slow AoE skills like Meteor Shower. Some defensive skills like Ward Against Melee are very useful when the team doesn't have a main Elementalist with Earth Magic. Glyph of Lesser Energy is also very useful to lower the energy cost of some skills, such as Conjure Nightmare.
Assassin may be used for some defensive Shadow Step skills, as well as some enchantments. Also, using daggers with Dagger Mastery (for the double strike chance) is a decent choice for IW mesmers using Illusionary Weaponry.
Ritualist is useful for the same reasons as the monk: better self defense and a hard res.
Paragon is quite uncommon, since paragon chants do not take advantage of Fast Casting, though some of the Shouts of Chants can still be useful for the team as a whole.
Dervish has few skills which are slow enough to take advantage of Fast Casting and thus isn't a common secondary. That said, some Dervish skills (like Mystic Regeneration, Mirage Cloak or Conviction) can be useful for improving the Mesmer's resistance.