Secondary professions for a Dervish

Dervish Warrior
Armor-boosting Tactics skills make good additions for fragile Dervishes. "Victory is Mine!" works well with condition-causing Dervish skills.

Wild Blow is also very often used by Dervish/Warriors, while not using any other adrenaline skills. This skill is especially good at ending stances like Escape, Dodge, Defensive Stance or Dryder's Defenses.

Dervish Ranger
This combo yields little benefit for a Dervish primary that other secondary professions can't provide.

Dervish Elementalist
Grasping Earth provides a snare.

Dervish Mesmer
For farming or mass AoE damage, another good combination is Signet of Midnight (which also blinds the Dervish) coupled with Epidemic for spreading blindness. Using Sand Shards while blind makes way for repeated, heavy damage. Since Signet of Midnight works for the same time it recharges (15 seconds), one could technically farm forever, with only Faithful Intervention or Watchful Intervention for healing. Whirling Charge can speed up this process as well.

Spending a lot of time casting enchanments in the middle of a melee fight, a Dervish could make use of Channeling. With this cheap and long lasting enchantment and Mysticism, the character would gain energy both when the enchant starts and stops. However, Channeling is a Prophecies skill, so it's not available from instructors in Istan (at least).

Dervish Monk
Probably this could resolve in a nice combination of Mysticism combined with Protection spells to get massive amount of energy back from your cheap protective enchantments. Contemplation of Purity could quicken this, and since many Dervish enchantments give a Dervish even more health upon ending, incredible spike heals and conditon removal is possible. Healing Prayers spells are less useful, however. Dervish already have several self-healing skills that can equal or surpass the healing skills typically used by a melee/Mo combination.

Many smiting skills involve point blank Area effect damage, so could be a useful addition to dervish damage. Many smiting skills are also enchantments, making them useful for powering other dervish skills.

Dervish Necromancer
Like any melee character, the Dervish could use Plague Touch.

Aura of the Lich could also prove to be of great use for a Dervish (instant healing in combination with enchantment removal skills, in addition to its usual effect). For "blood-drinkers", Blood Renewal can also do the same job, without taking the elite slot.

As a condition-dishing machine, Dervish player can find Tainted Flesh or Poisoned Heart (if quickly removed) quite an interesting alternative as well.

Dervish Assassin

 * Shadow stepping Skills such as Shadow Walk are useful to teleport up to casters in the back lines.
 * Shadowy Burden's snaring and armor reduction effects combine well with Vow of Strength.
 * Dash can be used as a no-attribute speed boost.

Dervish Paragon
Remedy Signet can be used as an alternative to Mending Touch in energy-intensive builds.