?: Does the Angel of Vengeance T1 PRE which gives a -2 to AC stack with Unbalancing on an item when it procs?

Leveling an Evoker FvS with Bloodrage MFP of Invul and looking to add Unbalancing to my Mod Fort ring if it will further decrease mob AC when mixing it up in melee.

Realizing that once I get BB things will go much faster but there are those times when you want to go toe-to-toe with something and every little bit helps.

Anyone know from experience or have a theory?

Thanks,