It’s simply too strong and makes one trait more favorable than another.
#1 - Unlike stun and impair, there’s no real counter to it. Now that active skills are a thing, stun and impair have been significantly weakened while absolute defense hasn’t received any type of nerf.
2 - Absolute defense gets activated on average, per raid, more than any of the other top weapon specials .
#3 - It’s a much stronger version of AP down. If someone has huge ap when attacking on defense and strikes a toon that has AD and AD activates, that toon has essentially lost a whopping 42 AP.
They’re a few more reasons AD needs to change but I’ll just mention the 3 reasons above.
I know people will want AD to stay the way it is because of how they feel about nerfs, but there needs be some competitive balance.
Just a minor suggestion but perhaps AD should just be a % damage reduction. An 80% reduction to damage sounds about right.