Once the commands behind those addons were destroyed by Blizzard, Overhealing took on a whole new cult following. Visualize, if you will, a 40-man raid with 10 healers and 3 tanks. Imagine how many of your heals would land a split second behind someone else's. Also back then, the healing to hp ratio was pretty high but healing to total mana pool was not (i.e. you could heal a big chunk of a tank's total health, even with downranking, but you didn't have the mana pool to keep it up). You would see the fabled "Healing Rotation" where healers would take turns solo/duo healing a tank until they went OOM. Then the next healer or two would step up, while the first stood there, letting mp5/spi do the work. For some bosses you could have 6 healers in rotation so you could make it to the end of the fight.
After months of heals being written over and precious mana being thrown in the trash while 40-man raid healing, many healers developed the mental condition healus overexia, where they would wait until they were 100% sure a full heal would land before they even thought about casting. And then they'd wait a split second more to really be sure... you know... just in case. But it was ok. You had 9 other people covering the things you wouldn't.
Enter the Burning Crusade. Suddenly your mana pool is great (I just about passed out when I hit 10k mana) but can you ever imagine solo/duo healing a MT, like for Magtheridon? Nope, me either... at least on purpose. But to those with healus overexia, nothing had changed. If anything, it got worse as random spike damage healing became the name of the game. Healers started literally stacking heals in the hopes to take the edge off. And even then, you still need a few people jumping in with big heals to top off the tank.
It was also at this point where having healus overexia became quite noticeable to the rest of the healing group. I can recall one frightful day when I went completely OOM raid healing. I glanced at my assignment partner and noticed he was at 94% mana. And by noticed, I mean my eyes bugged out from my head while I madly clicked on my mana pot button, hoping that would somehow speed up the cooldown timer. So I started watching my partner's character, since we were beyond the point of winning anyways. There wasn't any casting action that I could see, except for the occasional heal on someone nearly dead. Yelling out over Vent "ZOMG WTF ARE YOU DOING!?!?!" seemed uncouth, so I chose to talk to my partner later privately. In a dark alley. With my lead pipe.
This is where I discovered there is both no absolute cure, nor an argument that will convince those with healus overexia that what they're doing is hurting the team. In their minds, it's all about the numbers and the lower the Overhealing, the better. Raiding became more about the different ways they could conserve mana than actually healing people. They were meta gaming Overhealing as the most important stat, even when their actual effective healing was lowest of the bunch (much lower). In the end, I had to throw my weight around as "she who controls your raid life" before my partner would change their ways.
Why tell you all this? Because not everyone has healus overexia and if I can prevent this malicious disease from spreading, I'm willing to do my part. Roll up your sleeve and prepare for mental inoculation. Overhealing isn't a bad thing, but a necessary evil for the raiding environment we're tossed into every week. With mana being important but no longer the constant limiting factor, Overhealing has transformed from indicating how good you are at conserving mana to how proactive you are against random spike damage.
What? Yes, I use Overhealing to make sure healers aren't being too reactive to damage (starting to cast once the damage has already landed) and instead are trying their best to keep ahead of the game. Of course, I still don't want to see extreme amounts of OH due to people being too lazy to cancel casts. But if you're being 100% reactionary, you're going to lose people to spike damage that otherwise would have lived. An early 25-man raid example would be the OT on Gruul. You don't want to suffer the embarrassment of having the OT die because you weren't queuing up heals and a Shatter got him. Later in your 25-man raid life, Mother Shahraz will hang you on a flag pole by your unmentionables if you aren't proactive on the MT. There are a ton of other examples out there, too, and not just on bosses.
So how do I figure out how much OH is reasonable? For a given fight, I first evaluate how I'm honestly healing. Normally I'm fairly proactive on tanks, with the occasional "Oops, I should have cancelled." cast getting through and some downranking going on to match the damage I expect. But some nights I'm really tired and I know I wasn't even trying to cancel my casts. Seriously consider how you've been doing.
Next I pull up my Overhealing numbers and compare mine to other healers. The key here is I not only am in the same fight as they are, I give out the assignments so I have a good idea of what everyone's facing. I use myself as a reference and see how they did. If I feel like I should be a good baseline, then I would expect everyone to be around where I was. If I was having a seriously crappy night, then I'd predict people to have lower OH. I also take into account assignments, especially if some people are on a tank that has the potential to be one-shotted. They're going to have higher numbers (hopefully).
Also, don't forget classes with HoT's/PoM/Chain Heal. These are self-policing heals that should skew their OH numbers lower than say Paladins, since those types of spells only heal if there's healing to be done. The goal here is you don't want to see any crazy outliers. Everyone should be fairly close to each other (like 5%-10%) by class. Lastly, never EVER confront someone based on a single fight or even a single raid unless you actually saw them doing something terribly wrong (per my story). For all you know, their cat could have caught fire during the run and they were a bit distracted. Ask what was going on first and have a plan for correcting the issues before plunging into your breakdown of exactly how they suck.
A lot of people have asked me "What are some good, general Overhealing numbers?" For the early 25-man stuff up through the last couple of bosses in SSC/TK, I'd say if you aren't around 20% to 30% Overhealing, you're probably not being as proactive as I'd prefer. If you're down around 10% you're just flat out not casting enough and healus overexia has set in (I don't think WoWWiki raids much, since they're reporting the ideal numbers for back when Mana Conserve was golden. Honest.). For MH/BT, some of the bosses require anywhere from 40%-50% OH, depending on what's going on.
Where did I get these numbers? I do random spot checks, plus some actual baselines taken over a month of raids when I came across healus overexia in my own raid group. The ranges I indicate were pretty consistent with downing bosses. If we did much less, tanks would die and we'd wipe - much more and mana would become an issue. On the heavy OH fights in BT, all the healers are maxed out on mp5 consumables to survive. I've also done some spot checking of the Elitist Jerks WWS thread. Without knowing who had what assignment, all I'm looking for there is order of magnitude, and they match up nicely to what I see in my raids.
If you gasped for air at my OH numbers, I recommend trying to breathe slowly. In through your nose, out through your mouth, and that sort of thing. Now remind yourself of all the things you didn't have in BWL: Vamp Touch, +10k mana, mana saving/adding spells (i.e. Shadowfiend, Divine Illumination, etc.), high mp5/spi. Really, we can work through this... Meet me in the alley at 10pm. I'll bring my lead pipe.
P.S. Please vote here for the Healers! The DPS are totally kicking our butts but we got this, guys!
Marcie Knox has been healing lead for over a year, including old school AQ40/BWL/Naxx. She has suffered through holy priest and now basks in the glory that is healadin. Her pally is currently marveling at the frickin' laser beams attached to Illidan's frickin' eyeballs. Seriously, eye beams better show up again in the Sunwell.