The layers of armour that could be given True Armour were reduced a lot and now weapons can be runed and enchanted (with activatable locks) far higher than before. I would say this is a moot issue now...you can definitely crit through full armour and high level combat is usually decided in a few rounds...5-6 rounds is often quite decisive.

To more directly answer the question, I would say no. Especially with weapons and combat levels as they are now, a hit that bypassed armour entirely would certainly be an immediate kill. We already have "IK" chances built into the critical hit system. And as I mentioned above, being unable to do proper damage against full armour is no longer an issue.