better thief armor/spider armor

I feel that thief armor doesn't get what it deserves, and the unique spider armor can be perfectly replaced by effects on mystery armor. the whole point of unique gear is for them to be different, special, and useful in their own way. having mystery armor that is an exact copy of unique spider armor makes it not special, and I think that takes away from the full potential of the armor type. 

an example of possible upgrades to thief armor are movespeed aura, or even a new dual wield proficiency that makes things like sickles and daggers more powerful.