Ah yes, I almost forgot the near-uselessness—and indeed likely additional hindrance—of armor in virtually any PvE fight that's remotely difficult, especially at NG+ strength and beyond. Phantoms are perhaps an exception, because they're PvP-like and Poise also matters.
Fully upgraded Havel's with a Ring of Iron Protection +2 and high defensive stats will reduce a physical blow by, at most, 120 points of damage on average. When bosses that matter are smashing you for a bare minimum of 600 HP per hit, assuming you have 2,000 HP for simplicity's sake, this will allow you to take probably (but not necessarily) one additional hit before dying. The price you'll pay for this is an absurd investment in VIT that could simply go to more health, stamina, mobility, and damage instead, and even then your mobility will be severely reduced. Astronomical amounts of VIT are required to wear full Havel's and other gear and rings while not fatrolling.
That's with the toughest armor in the game. Thing is though, many bosses incorporate elemental damage, and the range of elemental protection isn't nearly as high even on the heaviest armors. So, in reality, you'll generally be taking at least 4/5ths of the total damage even in extremely protective armor with specific elemental rings.
As for Poise, it's really only useful for slogging through (some) non-boss PvE and in PvP. This is because the hardest bosses deal approximately infinity Poise damage, with minor exceptions such as possibly not being staggered by a single hit from the Fume Knight's longsword (what an advantage!).
Anyway, I knew all this going in. When I switch to my non-upgraded farming gear with zilch defense (Jester's Cap, Jester's Gloves, Prisoner's Tatters, etc.), I barely notice a difference and that's versus NG regular enemies.
Magic and armor clearly have to be shit so that we can have a rolling, backstabbing, and bow-sniping simulator, apparently because people need to brag about memorizing when to roll because that's the most highly skilled thing of all time. When I finish my no-hit naked Fume Knight run and post the video, you will all be obligated to bow down to me as the thread master and expert on all things Dark Souls, the most skilled individual ever to live and clearly the 1337est.
I'm going on vacation this afternoon though, so it'll be a while.