One fun factor is that warrior self healing is based entirely on our health. The more health we have, the more we are healed when healed for 10% of our health. And the more health we gain when we pop Last Stand.
Accuracy gives you increased rage flow, but depending on the content and gear level and play style, it's possible to have more rage than you need or can use without HS/Cleave well before you are accuracy capped.
Mastery only adds a minimal amount of passive mitigation, but it greatly improves active mitigation value, and helps to mitigate the rage cost of Shield Block.
Avoidance adds a decent bit to passive survivability, but only to your active mitigation via Revenge procs, and you can easily reach a point where Revenge procs for more frequently than you can use it. It also means the rage generation is dependent entirely on how fast the avoidable hits are coming in.
Given that your active mitigation is considerably more powerful than your passive survivability, it makes sense that if you only have enough in the budget to maximize one, you go for active.
Throw all that in the blender and the end result is pretty much
stamina (to safe from burst point) > hit & expertise > mastery > avoidance
with the caveat that the specifics for hit and expertise depend on how comfortable you are with rage flow, as they are the stats that have the most direct impact on it.