30% increased Damage while in Blood Stance, 15% increased Area of Effect while in Sand Stance
10% more Damage with Hits and Ailments against Enemies that are on Low Life
Attacks with Axes or Swords grant 1 Rage on Hit, no more than once every second
If you have "gain 1 rage per hit up to once per second" from a cluster jewel, and you have the axe mastery that does the same, will you now gain up to 2 rage per second?
Each of those effects has its own entirely separate limitation. You can gain 2 total rage within a 1 second timeframe - 1 rage comes from one effect and the other rage comes from the other effect. Neither effect can exceed its own limitation, but neither of them knows about the other. They're entirely independent.
How to allocate Axe Mastery?
Allocate a Notable Passive Skill in this cluster, then this Mastery becomes available to allocate in the cluster.
Spend a passive skill point on the mastery, then choose a specific stat to gain.