Resource pooling

Resource pooling is an advanced tactic used by non-mana classes to make the most of their abilities. The idea is that when a limited-time bonus effect is active, the maximum amount of resources - whether rage, energy, or focus - should be available in order to use many abilities in a row, causing them all to benefit from the bonus. This is generally used by players who have already mastered their specialization's basic rotation of abilities and reactions to fight events, to push their effectiveness even higher.

Resource pooling could be considered a subset of the idea of "stacking" beneficial effects, except the "effect" being stacked here is "having many resources to use abilities rapidly".

Resource pooling is mostly a strategy for damage dealing. Tanks are not usually interested in "spamming" abilities in the way that pooling allows, while healers have large mana pools that normally do not require pooling.

Applicability
Abilities and other effects can be roughly categorized by their synergy with other abilities and their level of "uptime", both of which affect resource pooling potential. Personal or raid buffs, enemy debuffs, or even encounter-specific mechanics can all be considered "buffs" for the purpose of resource pooling, as long as they increase the impact of other abilities. Note that pooling might turn out to be irrelevant to a buff that theoretically would benefit from it, because the specialization's rotation has higher priority concerns or is otherwise too complex for pooling to be a factor.

Some abilities have no impact on the effectiveness of anything else, for instance simple direct damage. There is no reason to be concerned with resource pooling before using these attacks. However, such abilities may be affected by others, and some of those may benefit from pooling. In many cases, this type of ability is the mechanism by which resource pooling does its work, by allowing these "standalone" attacks to be used more rapidly.

Low-cooldown buffs that enhance white damage or increase haste typically are desirable to keep up all the time, since white damage is dealt nearly constantly and haste speeds up the entire rotation. Because such buffs should be constant, there is no "effectiveness window" for which to prepare by resource pooling, and so the strategy is irrelevant. At most, a player may want to reserve enough resources to refresh the buff when necessary, but nothing more. This rule is not set in stone - it depends on whether the effect's across-the-board benefits outweigh the benefit to resource-costing abilities that could be pooled.

If other resource-driven abilities are the primary beneficiaries of a low-cooldown buff, then usage is simple - that buff can be applied whenever it's convenient to stockpile resources. That stockpile would then be consumed by all the abilities that benefit from the buff.

Many cooldown-driven abilities are desirable to use as often as possible. Therefore, players should anticipate the expiration of the cooldown and begin pooling resources beforehand. When such a cooldown becomes available, it and a large number of abilities can then be used immediately, and the cooldown can begin ticking again with no delays.

Usage
In practice, due to reaction time, lag, and the global cooldown, it is generally not realistic to wait until the absolute maximum resource cap, especially with a resource that regenerates quickly, since any delay after reaching maximum would cause potential resources to be wasted. Players may instead want to aim for a "soft cap" where there is still about 1-1.5 second's worth of "room" before hitting the maximum and wasting resources.

It is easiest to pool energy if a player has control over the timing of the buff period, such as one granted by an ability or on-use item, but it is also possible in response to random or timed events.
 * When pooling resources for an on-use ability, players can simply use the ability upon reaching the "soft cap" target.
 * When waiting for a random effect, such as a trinket's random activation, a player may have to maintain a high level of resources for a number of seconds, by first reaching the target "soft cap", then using a single ability (preferably a low-cost one, but the ideal selection depends entirely on the class and specialization), waiting to reach the cap again, and so on until the desired effect is triggered and the resources can be "unloaded". This ensures that even if resources are not at a cap when the effect goes off, they will at least be close to it.
 * When attempting to pool resources for a timed effect in a fight, such as a high-damage phase of a boss encounter, or even the cooldown of one of their own abilities, players will want to estimate when the phase transition or cooldown will occur and start pooling resources early enough to reach maximum by the desired point. Addons as well as cues within the fight may help with this, but it is often necessary to allow for several seconds of error in either direction by starting pooling even earlier, and being prepared to maintain near-maximum resource levels for several seconds until the timer triggers.
 * Coordination with or attention given to players that grant raid buffs is often helpful. For instance, if you know when a warrior ally will use Skull Banner, it may be beneficial to pool resources beforehand to try to get as many critical strikes as possible while the banner is active.

Special consideration must be given to effects that increase the rate of resource regeneration, including fight mechanics that slow resource consumption, even simple movement. If the increased net rate of regeneration is likely to cause the player to hit the resource cap, then the energy should obviously not be pooled to maximum beforehand. The combinations of effects that cause this situation vary from class to class and fight to fight, and again can be affected by lag and reaction time. If the only benefit of an effect is to increase attack speed and/or resource regeneration (e.g. a bloodlust effect), then there is no reason for pooling, since there is no synergistic benefit to be gained and resources may even be wasted. However, since other cooldowns are often saved for such an effect, it may well be worth pooling energy for those.

Example
A combat rogue's Revealing Strike increases the effectiveness of other abilities and lasts 24 seconds. If it is used as soon as possible, the rogue will have 0 energy after using it, and will regenerate 300 energy in the next 24 seconds (not including random energy effects), allowing the use of 300 energy worth of abilities enhanced by that single Revealing Strike. However, if a rogue stops using energy-consuming abilities briefly and waits until 100 energy to use Revealing Strike, 60 more energy will be available for enhanced abilities during the duration of Revealing Strike, a significant increase. This saves energy and time that would otherwise be used reapplying Revealing Strike more frequently than necessary.

Other resources
Mana-using classes and specializations generally have no reason to concern themselves with resource pooling, since the very nature of a mana pool means they should already have all the resources desired. However, a similar strategy to traditional resource pooling may be employed if such a class finds itself low on mana. In this case, instead of casting a series of ineffective spells one at a time as soon as any mana is available for one, it may be beneficial to wait until enough mana for several spells is available, so that positive interactions between spells can occur and the scarce mana can be used as efficiently as possible.

Charge-type resources, including the death knight rune system, are typically too inflexible to be "pooled". Since there are so few possible states for them to be in, it is difficult to pool a meaningful amount of them without hitting the "cap" where potential recharging is being wasted. Such charges are also usually quite restricted in their generation and usage, so it would be difficult to change their timing without reducing their overall effectiveness. This limitation is reduced with more charges and more flexibility in their use - for instance the rogue Anticipation talent effectively doubles the number of combo point charges, and stops them from being completely consumed by every relevant ability, thereby turning them from a relatively predictable cyclical resource into one that can be pooled for specific uses.

Other bar-type resources such as Demonic Fury may well benefit from pooling, depending on the abilities and effects available.

Other meanings
"Resource pooling" may sometimes refer to other situations in which a buildup of resources occurs, even if they are not being specifically saved for a large expenditure as described above.

One reason a player may do this intentionally is to reserve resources for use when a random effect grants a charge of an ability, or for when an ability's cooldown ends. Note that unlike full resource pooling, the objective is not to maintain near-maximum levels of a resource for subsequent "dumping", it is only to reserve enough of it to use the anticipated ability(s).

It is also possible for players to unintentionally pool resources if a combination of cooldowns, random effects, or fight conditions prevents them from being used. This may look similar to strategic energy pooling, but unless such players are lucky enough to have an applicable ability ready to exploit the buildup of resources, they will likely not see any benefit, and may end up wasting resources hitting the maximum.

List of abilities
These rogue abilities benefit from energy pooling:
 * Shadow Blades
 * Kidney Shot, to pay for more Backstab uses (subtlety) and also for more abilities benefiting from Prey on the Weak (talent)
 * Subtlety:
 * Shadow Dance and Vanish, to pay for more stealth abilities and for more abilities to benefit from Find Weakness
 * Combat:
 * Revealing Strike
 * The Deep Insight (maximum damage) phase of Bandit's Guile
 * Assassination:
 * 35% target health, to pay for more Dispatch uses
 * Vendetta

These warrior abilities benefit from rage pooling:
 * 20% target health, to pay for more Execute uses
 * Recklessness
 * Skull Banner
 * Avatar (warrior ability) and Bloodbath (talents)
 * Colossus Smash (arms, fury)

These feral druid abilities benefit from energy pooling:
 * Tiger's Fury, but treating 35-40 energy as "maximum" to avoid wasting the energy from the ability itself
 * Berserk, increasing the number of abilities that can be used at reduced cost
 * Ferocious Bite, but only enough to ensure the maximum of 50 energy is consumed

The beast master hunter ability Bestial Wrath benefits from focus pooling.

The engineering tinker Synapse Springs (Mark II) benefits from resource pooling.

Players can gain an increased effect by pooling their resources before this ability from other players:
 * Skull Banner (warrior)