From WoWWiki

The third and most unusual Hunter talent tree.

Overview

"A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects." — Robert Heinlein

"People are frightened by what they don't understand." - John Merrick, The Elephant Man.

The Survival tree is designed with the worst possible scenario archetype in mind. In both PvE and PvP, it emphasizes a more defensive and utilitarian overall strategy, as well as being unique in providing a balance between ranged and melee attacks. From the beginning, talents that increase damage via melee attacks contrast with the ranged talents of like nature in the Marksmanship tree, in particular. However, near the middle and further downward, the unorthodox tree moves in a direction all its own, breeding one of the deadliest (if rarely used) character builds in the game. Unlike Marksmanship or Beast Mastery hunters, a Survival hunter is actually designed to handle enemies that get into his melee range- even more since patch 3.0.2, with Scatter Shot now in the Survival hunter’s arsenal as well.

To explain this further, the Beast Mastery talent tree is offensive; it relies on overwhelming direct damage output to subdue enemy players or mobs. By contrast, Survival, as it’s name implies, is largely defensive in nature, and is also therefore designed to deal with opponents that are capable of superior force. The real-world military term for this strategic philosophy is attrition. A Survival Hunter will typically have substantially more base health than a Beast Mastery or Marksmanship hunter. A number of combined, low-power (and by themselves, relatively non-lethal, such as Immolation Trap, Snake Trap, and Serpent Sting) attacks, and various diversionary tactics (such as Freezing Trap, Feign Death, Disengage, Misdirection, and Wyvern Sting) are used to both precisely control the flow of battle, and neutralize opponents by gradually grinding them down over time.

The benefits of this approach are greater mana efficiency, more regulated threat generation against mobs in solo PvE, (given that Survival is a crit based spec, using the more typical mana shots can result in threat spikes. Relying on traps, stings, and then simply Steady or straight Auto Shot reduces this risk, as the damage becomes a more gradually sustained form rather than burst, so the pet can keep up) and a greater number of potential options for countering specific tactics that are being used by an opponent.

The major disadvantage however is that such an approach is time based; enemies who are able to generate rapid, high powered burst damage (such as Frost Mages with Ice Lance) can prove overwhelming.

Patch 2.1.0 revitalized the tree, buffing several talents (including Expose Weakness, which was bumped to a 100% proc). At the time, however, only 7% of hunters had more than 50% of their talent points invested in the tree. It was further improved with the release of Wrath of the Lich King, with the addition of many talents that greatly increased the tree’s offensive potential, (ostensibly) bringing it in line with the other trees.

With DPS approximately equal (again, ostensibly) to the other hunter trees, and higher base health, Survival finds its balancing factor to be it’s complex rotation- more so than Beast Mastery or Marksmanship.

As of patch 3.0.8 (and the nerfs to Beast Mastery it brought), many, many hunters are trying Survival for the first time.

Strengths

• Very high DPS.
• More effective at killing plate-wearing classes than Beast Mastery or Marksmanship-specced hunters- the survival hunter's most damaging ability, Explosive Shot, causes purely fire damage.
• Augments survivability through increased health and resistance to snares.
• Emphasizes balance between ranged and melee ability, by including talents that enhance both.
• Copes more effectively with multiple targets than either of the other two Hunter specs, including Beast Mastery, due to strong crowd control which enables sequential execution.
• Encourages, out of necessity, a fairly extreme degree of intimacy with the Hunter as an overall class. The tree doesn't really give you much of a free lunch at all, especially not low-level. Because of this, you'll either become a genuinely skilled Hunter, or a repeatedly dead Hunter.
• Enhances the Hunter's trainable traps.
• Designed to be effective at coping with melee targets at minimal (just outside melee) range. The tree also provides an outlet for hunters looking to stay a little farther away, with talents like Sniper Training and Hawk Eye.
• Allows greater mana efficiency (Thrill of the Hunt, Hunting Party) than the other two trees.
• Emphasizes burst damage via both melee combat, (Savage Strikes) and ranged (Lock and Load). All of the tree's bonuses to critical strikes apply to both ranged and melee damage.
• It scales better with gear due to Lightning Reflexes, Expose Weakness, Hunter vs Wild, and the Attack Power bonus of Survival Instincts all being percentages.

Weaknesses

• Somewhat more oriented towards high level or close to end-game use.
• Considerably more difficult to use effectively than either of the other two trees.
• Because of how often survival hunters pull off their pets, using the spec for leveling or soloing in general is comparatively slow, with downtime for eating required more often than the other trees. This will likely be seen as a drawback by the impatient.

For a detailed synopsis of Survival talents, including percentages and additional information, see Survival section of Hunter talents.