Most likely item candidates to get a hard look at during the Vanguard update, based on what Riot said about tanks being too resilient to sustained physical damage and too vulnerable to sustained magic damage and, as you said, some tanky damage dealers not being too healthy. Source - Preview of the Long Term, part In-game systems and Champion Changes.. Note that these are just my opinion on this stuff:
: The most common Armor item right now. Suspect that it is simply overtuned and giving too much stuff for the single item slot it occupies.
: One of, if not the, main culprit for tanks' high resilience to sustained physical damage, with its passive that reduces auto-attack damage by 12%. Could see Riot simply reverting the buff they gave the item a while back, when they changed the passive from 10% to 12%.
: My qualm with this item is that it shifted from being an all-purpose item that gave a mix of sustained (AD, AS, Crit) and burst damage (Sheen proc) to one that gives mainly burst damage, both in a higher intensity (200% base AD proc) and with higher frequency (20% CdR). I hope that Riot sees this as well and takes a bit of power out of the Sheen proc and CdR and back into the sustained damage (possibly by swapping Stinger for Recurve Bow).
: The only real tank MR item at the moment. Either will it be changed somewhat, or Riot might introduce a new tanky MR item.
: Since it is the Vanguard update, this item might warrant a look.
: Despite a lot of buffs over the years, this item is still not commonly seen. I really wonder if it was possible to turn into the true tank's staple, something akin to what Infinity Edge is (or is supposed to be) for ADCs or Duskblade for AD assassins.
: If it gets any attention, changes to this item should be made rather carefully, as its passive effect is still one that increases the amount of burst damage in game (and thus contributes to the burst damage creep). Crazy idea: what if the passive was change to give an increase in attack speed instead of damage? Shifting it away from burst, into sustained damage...
: Obviously.