Bug: Exactly as it says in the title.
Situation: I was derping about in Solo mode last night in Steel Path Incursions after an SP Circuit run with my Ack and Brunt (doing the third and fourth Incarnons), Soma Prime (full Incarnon), and Laetum (Incarnon level 4, because I don't have the original Incarnon weapons yet and was seeing if the new ones counted for the last node, they don't). I noticed that not only did my Iron Skin feel weak (that was my fault, was using my Starchart build), but also all the procs that Iron Skin usually blocked went straight through. After getting bodied repeatedly by the Infested and Grineer, can confirm all IPS and Elemental effects go through, as well as Knockdown and Knockback. All Acolyte and Juggernaut abilities work, too, which was fun to find out about at the same time.
Repeatable: Yep, seemed to be all the missions I played with Rhino before getting salty. :D