Do banners, shouts & warhorn all stack?
Boons say what stacks,
Fury stacks duration, as does swiftness, might stacks power as does confusion, vulnerability, bleeds, etc.
No boons cancel each other as far as I know…
Note that warrior banner buffs do not stack with the same type of banner. They have a different icon than boons, and do not follow the same rules. So 2 banners of defense in the same area isn’t giving any more benefit than one.
Tarnished Coast
I have tested this but it seems that the warhorn may cancel out one of the other boons or vice a versa. Sorry just having a bit of a time figuring out what stacks with what. Now if I throw in runes, etc. it gets very confusing for me.
Wishes
Read the Comprehensive Bug List at the top of the Warrior forum page regarding warhorn and Signet of Rage (Swiftness).