Hey all, I'm Swol, the main theorycrafter at Ask Mr. Robot and the person responsible for most of the rotations, stat weights, etc. on the site.
I've made little posts here and there regarding our resto druid weights. This will be a compilation of a lot of the reasoning that goes into healing stat weights in general, as well as resto druid in particular.
Part 1: Max Theoretical Healing vs. Topping the Meters
Part 2: Haste and Mastery for Resto Druids
Part 3: Why not stack HoTs in raids?
Part 1: Max Theoretical Healing vs. Topping the Meters
Healing is a fundamentally different problem to solve than DPS. For DPS, there is no limit to how much damage per second you can do. The fight will simply end sooner if you do more damage. For healing, there is a limit to the HPS you can do: the damage the raid takes. I will start with an example I like to give, which illustrates why healing meters can be very, very misleading for healing theorycraft:
Assume your raid takes 400,000 damage per second, on average. Now, assume you have three identically geared and skilled healers each capable of putting out 150,000 healing per second, on average. Their potential is 450,000 healing per second. But... you don't NEED that much healing. It is very rare that those three players will all be able to do 133,333 HPS on the fight. Assuming they are all playing different specs, chances are that one of those healers will be good at snagging small amounts of effective healing the fastest, allowing them to do 150,000 HPS. So, now the other two healers are left doing 125k each, making them look like they aren't playing as well. It is very rare that you need exactly 3 or exactly 4 healers on a fight. You usually need 2.75 healers, or 3.5 healers, etc. This is why healing meters and especially healing log rankings are almost completely worthless for measuring performance or theoretical stat analysis. Topping meters is a fun meta game, but, we have to admit that it is just that: a meta game. You can be a perfectly effective, skilled, and useful healer without topping a meter.
This leads to a situation where healers are competing with each other to grab the effective healing first, so that they look the best on the meters. Another consequence of this situation is that people will start to gear in such a way that they are able to be the first one to heal people. The stats that could get you the most healing possible over the course of a fight might not be the best stats for being the FIRST one to heal people on fights. Resto Druids are an extreme example of this in Legion.
Part 2: Haste and Mastery for Resto Druids
Haste is a tough stat to deal with in healing theorycraft. Its value depends heavily on how long a fight is. On longer fights, you are limited by mana, not time, thus making the ability to cast more spells pretty weak. But, resto druids heal almost exclusively with HoTs. As we know, HoTs actually get a throughput increase from Haste independent of the quantity of HoTs you cast. Each HoT will actually do more healing over its fixed duration.
What else does Haste do for us? It helps us top meters. More haste on all those HoTs that are all over the raid also translates to increased heal frequency. All of those HoTs are excellent at snagging up small bits of incidental damage FIRST. This makes you look great on those healing meters.
Mastery for resto is new in Legion. You do more healing per HoT on your target. This stat offers the potential for extremely high theoretical healing throughput. Mathematically, it is the superior stat for resto druids. But, of course, it depends on you playing in such a way that you are stacking HoTs on targets instead of spreading HoTs around.
This leads us to the root of why "they" recommend Mastery for 5 mans and Haste for raids. In a 5 man, you don't have anyone competing with you for the available healing. It's up to you to do everything, giving you maximum opportunity to stack HoTs. In raids, most of the time we are more or less playing wack-a-mole with our raid frames as fast as we can. Putting up HoTs on whoever, wherever - actually fighting the other healers for heals a lot of the time.
Here are a couple of simulations that quantify the difference in healing you do when you stack hots in a 20 person raid, vs spreading them out:
A couple of notes regarding the simulations PLEASE READ THESE NOTES BEFORE LOOKING AT THE SIMULATION RESULTS:
1.) I used a 34 point artifact just to avoid biasing results due to the artifact path chosen, when you do your own simulations on your character, results can vary somewhat, but none of the artifact traits make a drastic difference in stat priorities. This also partially explains the very high HPS numbers you will see, though.
2.) This is assuming that all healing you do can be effective healing and that there is always someone to heal. There is no overhealing. Why? Because, I want to find out how much healing is possible, and which stats are best for that. If the raid doesn't need all of my healing, then I'm not going to be as concerned about what stats I use. In that case maybe I would just gear for topping meters.
3.) If you are doing your own simulations, note that cultivation is not yet implemented in the simulator. I hope to have health-based effects like that available next week sometime.
4.) I just picked some common talents. I am not in any way saying the talents chosen are necessarily the best talents.
5.) I didn't use any consumables and the rotation doesn't have bloodlust in it right now.
6.) The fight length is 6 minutes +/- 20% to approximate a fight that isn't crazy long, but not really short either.
7.) The "Haste/Crit" gear set I created by taking 8000 rating out of mastery and splitting it between crit and haste. I didn't change the actual gear, I just did a stat override to keep it simple.
There are two rotations I'm using for tests:
Max Healing - this rotation will stack HoTs on the tank and off tank, it puts efflorescence in the group of ranged players and uses wild growth on those players. AMR weights were calculated based on this healing pattern which leverages resto's mastery.
Spread Healing - this rotation will spread HoTs around the raid evenly and alternate using wild growth on the melee and ranged groups. It looks for players with no HoTs on them to heal first.
Simulation 1: Max Healing 840 Mastery-heavy gear set (440k HPS):
http://www.askmrrobot.com/wow/simula...8d4710a838b569
Simulation 2: Max Healing 840 Haste/Crit gear set (426.5k HPS):
http://www.askmrrobot.com/wow/simula...2408b9fafa9961
Simulation 3: Spread Healing 840 Mastery-heavy gear set (349k HPS):
http://www.askmrrobot.com/wow/simula...150680baa93749
Simulation 4: Spread Healing 840 Haste/Crit gear set (361.5k HPS):
http://www.askmrrobot.com/wow/simula...942f409acf6a08
So, as you can see: If you don't try to stack HoTs on targets, Mastery will be worse than Haste/Crit. If you do stack HoTs on targets, Mastery will be better. AND, you will do a LOT more healing if you stack HoTs on targets, regardless of whether or not you specifically gear for Mastery. This leads us to Part 3.
Part 3: Why not stack HoTs in raids?
We see now that when you don't stack your HoTs, you leave a LOT of healing on the table. Why would you do that? Why would your raid team do that? The amount of mana you have available in Legion is never going to go up significantly. We will be mana-limited on the harder, longer fights for the entire expansion. I think it is time we do away with the WoD-style spam heals everywhere mentality. If we look at the mastery of many of the healing specs, it requires some coordination to get the most potential healing out of each healer. Getting the max potential healing out of each healer makes the game more fun for the healers, as well as lets your team start to push towards doing content with one less healer.
Druids: Need to stack HoTs on targets.
Paladins: Need to be close to targets.
Shamans: Need to prioritize lower health targets.
Monks: Need to combo essence font and other heals on targets.
Disc: Needs to heal/shield first, then AoE heal through damage
Holy: Only one that doesn't really need a special play style to benefit from mastery.
I'm lobbying for people to take a look at their healing team and leverage their strengths instead of just "healing whoever". If you have a druid, why not tell your other healers to lay off putting HoTs on, say, the melee players and let the druid stack hots on them. The other healers can use their hots on the ranged players or tanks. Or, you could have the druid keep tons of hots on both tanks and tell other people to lay off them. Why not stand your paladin next to some people and make them more responsible for those players? It takes a little more setup, but, for people running with a regular raid group, even some minor coordination could result in significantly more effective healing.