Damage Reduction Scaling Incorrectly

I have no idea if this is just the stat being reported incorrectly or what.

As a Guardian Druid, more agility means your Ironfur contributes more armor.

If I lose 2.7K agility by taking my weapon off, and apply one stack of Ironfur I get this value:
114,719 Armor = 53.32% DR (53.43% against target)
I also get this exact value with a weapon that does not provide agility.

If I put my weapon back on and apply one stack of Ironfur, this is what I get:
117,758 Armor = 52.98% DR (54.08% against target)

I’m assuming the “against current target” is the actual reduction. The target being a Level 80 elite.

Can anyone figure out what’s going on here?