Do Azerite Traits stack and which ones?
Almost all Azerite traits stack.
The one exception is effects that “set” a value rather than modifying it. For instance there’s a hunter trait that sets Feign Death’s cooldown to 25s (among other things). If you have two copies of that one effect, FD’s cooldown will still be 25s, but the other things stack.
Static damage / healing / shield portions stack, percentage bonuses do not. There’s a very select few that don’t stack at all like the chance to summon dire beasts on kill command or the mini Fire/Storm Elemental.
It’s more complicated than that. Generally modifiers to power stack (unless they set it directly as mentioned), but modifiers to duration don’t, and there are other exceptions too. This can cause a lot of cases where it’s very beneficial to pick up one copy of a trait but only marginally useful or even borderline pointless to stack it, while other traits are very beneficial to stack.
Basically all X damage and such stat but if one says something like “reduces cost of skill by 40 seconds and gain 500 damage” then said skill will not go below that 40 seconds but the 500 damage will stack up to 1500 with 3 pieces.
They really should find a way to make this more clear in the game UI.
So the real problem is, they didn’t bother to indicate which traits are stackable?
Wish blizzard would but after the brainstorm nerf I wouldn’t really be trust them.
Most % bonuses also do not stack. Mainly those that proc or whatever. Like there is a Demo trait where HoG has a 5% per soul shard to refund. Having 3 of the trait doesn’t give you a 15%.