Some classes are built around pooling resources. That is, their abilities consume only a portion of their max, allowing them to use multiple of the same or similar abilities in quick succession, and allowing them to save resources when they’re not needed. Poolable resources act like a buffer against unpredictability or mistakes. Brewmasters are the classic example. They have three to four charges of brews, allowing them to use a few at the same time or recharge for later. They have ox orbs, which can be pooled during low damage times for a big heal at high damage times or small heals over time.
The ability to pool resources works as a way to mitigate risk. (“I don’t know how terrible the next 20 seconds might be, so I’m going to prepare for it by saving up resources.”) And risk in for tanks is often bad RNG, i.e. spikey damage intake, poor procs leading to less AM (less control), etc.
Vengeance has three resources as I see it: pain, demon spikes charges, and soul fragments.
Pooling Pain is limited by Soul Cleave’s max cost of 60. The most you can ever save up for is a combo of 2 Demon Spikes + 1 Soul Cleave, or one big Soul Cleave and one small Soul Cleave in succession.
Demon Spikes is limited by the 2 charges. When planning for risk, the most you can do is use the first charge to reduce the likelihood of bad things happening, and saving a charge for when the bad thing does happen or a special event calls for it.
Pooling of Soul Fragments doesn’t qualify as risk-mitigation because you can’t consume Soul Fragments and save them at the same time, like you can with pain and ability charges. You consume all that you have, leaving none to handle the next random danger. A buffer is necessary to manage risk, and there’s no buffer of soul fragments.
I go through all of this not because I think all resources should be poolable, should have a buffer, but that it seems notable that vengeance and brewmaster are so different here. Like, brewmasters are better at burst healing in a raid environment because they can pool ox orbs, which seems a little counter-intuitive on a class fantasy level. It’s also why I can play my monk at a higher level than my dh, because I tend to make a lot of mistakes but pooling my resources allows me to recover from them.
So in conclusion, why does a buffer (or poolable resource) reduce risk?
- a buffer allows you to use an item twice in succession, allowing quick recovery
- a buffer enables you to turn low damage periods into opportunities to prepare for high damage (i.e. recharge at low damage, use all charges at high damage)
- a large buffer means fewer opportunities for mistakes that lead to death.