Efficiency Efficiency is defined as " the ratio of the effective or useful output to the total input in any system " or , more colloquially , as " getting the most bang for your buck " . In World of Warcraft , nearly every viable strategy is based on some kind of efficiency , generally minimizing or maximizing some value or concept . This makes efficiency complicated as a topic , however , because any given process can be optimized more than one way . What is efficient in one sense may not be efficient in another . There are many ways to be efficient in World of Warcraft ; however when most people mention " efficiency " , usually they mean efficiency in one of the following ( related ) ways : Other effects , such as maximizing the damage you do per second , while technically a form of efficiency , tend to be referred to as " maximizing " or " optimizing " . Minimizing downtime . Downtime is thought to be the enemy of grinding . The less you have to travel or stop to eat or drink , the more you can focus on getting experience . Minimizing downtime is usually equivalent to maximizing XP per second ( or , more realistically , XP per minute ) . Some general tips on this : Mana efficiency when healing . A subset of mana efficiency is healing efficiency , and this is arguably the area where efficiency is the most important . If a healer is not mana efficient , he or she is likely to run out of mana before the fight is over and be unable to continue healing , likely resulting is player deaths and potentially wipe s . With the large number of healing spells , gear , buff s , and talent s that manipulate the math involved , it can be difficult to determine which heals are the most efficient . Further , there are multiple ways in which healing can be thought of as efficient . The two that tend to matter most are " hit points healed per point of mana " ( HPM ) and " hit points healed per second " ( HPS ) . Generally speaking , slower healing effects tend to cost less mana per point healed while faster spells such as Flash Heal and Lesser Healing Wave are less efficient , though this is not always the case ( Flash of Light being a notable exception ) . Spell power from gear serves to make things even more complicated , as some spells scale better than others with spell powers . For example , the druid spell Rejuvenation is relatively weak without any spell power , but scales to become one of the most mana efficient single - target healing spells in the game as spell power increases . As a general rule , however , spells which heal a lot per second ( high HPS ) will have fairly poor mana efficiency ( low HPM ) and vice versa . Fortunately , there are web sites that allow you to play with all of these values . Having a rough idea of the relative HPM and HPS of your healing spells is vital to doing a good job as a healer , as frequent use of low - HPM spells in the wrong situations will drain your mana , while using low - HPS spells in emergencies will lead to deaths . Many times , the differences between different healing spells can be summed up in terms of HPM and HPS . Mana efficiency when dealing damage . Determining the method that delivers the most damage per point of mana spent depends highly on class . Gear and talents also matter a great deal . The formulas used in determining damage are varied , and can be manipulated in many ways . See spell damage comparison for more information .