Is there a valid reason why rogue's daggers have armor bonus and mage's staff not?

[Vvildfire]

the staff decreases enemy armor by 20% each basic attack

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On the other hand daggers increase the player's armor by 10% constantly, as long as you auto-attack (which takes a fraction of a second)

Rogues don't have a shield/juggernaut, it's reasonable (pve player opinion)