Secondary professions for a Mesmer

Mesmer Warrior

 * Illusionary Weaponry with some combination of the IAS Warrior skills provides ample pressure damage, however, the lighter armor of a mesmer makes this a very difficult role to play.
 * Mesmers can also take advantage of superior energy regeneration to use the more energy-intensive skills within the Tactics line to mitigate damage.

Mesmer Ranger
This profession combination provides little benefit for a Mesmer primary.

Mesmer Elementalist

 * The Mesmer/Elementalist can take advantage of the Mesmer's Fast Casting attribute with the Elementalist's high damage spells to create large amounts of damage, but the lack of energy storage makes this style of play challenging.
 * Fast Casting can be used to take advantage of some of the timing-based effects offered by the Elementalist class, such as knockdowns with Gale or ensure Aftershock conditional damage.

Mesmer Monk

 * The "Resmer", a fast casting resurrection specialist, is a feature in some forms of PvP play.
 * Because Mesmers have many skills that affect Signets, they can accellerate damage using Smiting Prayers Signets.

Mesmer Necromancer

 * Me/N is a profession combination usually associated with specialization in status effects like hexes. This mix has access to a wide range of hexes from both professions, but care should be taken to ensure splitting attributes in this way does not hamper the effectiveness of these combinations.
 * Soul Barbs compounds the damage of the numerous Mesmer hexes.
 * Fragility along with several Necromancer spells that cause conditions, Especially Virulence, can be powerful.
 * Mesmer anti-melee hexes such as Spirit of Failure can be combined with Necromancer anti-melee hexes, such as Price of Failure.
 * A Mesmer can stack hexes faster than a primary Necromancer, due to Fast Casting.

Mesmer Assassin

 * Daggers, due to the chance of double strikes, have a "faster" attack speed than Swords and Axes, and so are better for Illusionary Weaponry. However, this is not a significant increase, and using them sacrifices the armor/health bonuses a shield may provide; also, assassins have no IAS of their own, which blunts the effectiveness of Illusionary Weaponry. Feigned Neutrality can be used while attacking with Illusionary Weaponry, ad your attacks never hit.
 * Assassins have a number of hexes that can expand a mesmer's effect, such as Shadow Shroud to assist spikes.
 * Aura of Displacement and Blackout could be used to shutdown an enemy monk from afar while being able to safely teleport back to your group.
 * Skill from the Shadow Arts line, such as Return, can help with a mesmer's survivability.

Mesmer Ritualist

 * Fast Casting affects both Item Spells and Weapon Spells, but not Binding Rituals.
 * Fast Casting can be combined with damage skills from the Channeling line to provide a fast spike.

Mesmer Paragon
This profession combination provides little benefit for a Mesmer primary.

Mesmer Dervish

 * The Mesmer/Dervish typically focuses on using Illusionary Weaponry in conjunction with a scythe.
 * Dervish protective and healing enchantments can be very helpful for mesmers who may find themselves hunted by opponents.