Over-healing is something a lot of healers look at to determine how well they do their job. Too much and it shows that you are very mana inefficient, and you dont really know really know what you are doing. For some classes (i.e paladins) over-healing isnt something too look at that much, but for other classes, like shamans it is very important. Now most of the time over-healing is the result of having a massive amount of incoming heals from other players (25m raids). With shamans having slow, but powerful heals, over-healing really hurts us. A tank might need your HW when you start to cast it, but by the time its finished they dont. Often times people dont know how to fix this. One solution that I've found is using a combat text addon that will show you how much of the heal gets wasted( I use MikScrollingBattleText). Lets say that I CH the tank, the effective heal is for 3500, with an over-heal of 10,000. This means that the tank and melee dps are getting heavy incoming heals. To minimize mana use and over-healing, use CH on the caster dps, often times they take damage as well and are ignored to keep the tank(s) alive. Another option is looking at the over-healing window in recount, however, I feel this isnt a good method unless you have time to look at the numbers and the technical crap it gives you.
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