Tanks serve a really simple function in principle, but a really wierd one in practice.
The principle is to control. Control damage output, where it is directed to, and positioning. The implementation varies from class to class. However there are two basic principles they all share:
1) Damage intake reduction. They should all take fairly similar amounts of damage, although the methods by which this is controlled may vary.
2) Threat output. All tanks should be able to output enough threat to keep the target focussed on them. This of course has to scale upwards to keep pace with DPS output from other classes.
I'm not going to examine the first one, I'll leave that to others. I'm going to focus on #2 - Threat Output.
The first big thing about Threat Output is that it needs to be fun. Now while fun is a subjective term, the universal truth of RPGs is that people like big numbers. Big numbers are awesome.
Now you could just say "Well then make tanks do 0 damage, and just generate threat numbers." That might be enough for some people, but the universal truth about MMOs is that people like competition. They need some way of comparing themselves to others. In WoW specifically this comes down to Damage, and Healing.
This means that just dealing Threat numbers isn't enough. Tanks need to do damage as well. However problems start arising when you need to be able to scale the Damage (and therefore threat) as content progresses along tiers. How do you pick a method to do this that allows your character to grow and progress, but doesn't hamper you or your raid's ability to clear content?
Blizzard has chosen to use something called "Vengeance". This increases a Tank's attack power by a 5% of incoming damage, up to a maximum of 10% of your Base Health + Buffed Stamina. Unfortunately there are inherent problems with this method.
The first and most obvious is that it doesn't scale backwards (or downwards I guess) as well as DPS does. By this I mean a DPS class will continue to do high amounts of DPS at lower tiers of content (be they raids or 5mans), but a Tank will not be able to do as much relative Threat. Of course you could always follow the "tank off your pants" method to solve this problem, but that shouldn't be necesarry. A tank should be able to generate sufficient amounts of threat to hold off equally geared DPS, regardless of the level of content they are doing.
The second is that any Tank that has mitigation that scales off of AP, cannot have their mitigation and threat independantly balanced while Vengeance exists. Increasing mitigation will decrease opening levels of threat, but increasing opening levels of threat to compensate for this makes the Tank completely overpowered at high levels of Vengeance.
I'm speaking of course, of Druids.
If we were to do away with Vengeance, we would have to find some other method of scaling Threat output with gear progression. So what does each Tank have in common with relatively similar values?
- Item Level
- Incoming Damage
- Outgoing Damage
Item Level is a pretty hokey concept, and I'd rather it remain simply a descriptor rather than an actual gameplay mechanic.
Mastery I like as a concept, but you could only have it increase the amount of threat generated, not damage. This seems to go against the concept of "fun".
We've already tried a combination of Health + Incoming damage, and look where that got us.
But what about Outgoing damage? It's much more constant than incoming damage, making it a much more reliable scalar for both future and past content. But how do you determine how it caps? Well, why not use the existing Vengeance formula?
That means 5% of your outgoing damage is added to your AP, with a maximum cap of 10% of your base health + your Stamina. Thia makes Vengeance:
1) Much more of an "active" scalar than a gear/encounter dependant one.
2) It becomes much more constant and reliable for threat generation. This makes it much easier to balance around.
3) Tank switches become less of an issue since both should be building up equal amounts.
4) Avoidance strings become a good thing and don't cause your threat to suffer.
5) It scales downward infinitely better than the current model.
The only problem is that it becomes more of a constant in PvP. The solution? Disable it when PvP flagged.
And no, I don't give a rat's ass if you want Tank-specs to be viable in PvP.
I'll be making a post later on about what could be done to balance or improve Druid threat specifically.