Have it, Whisper, and Voidstaff share a named passive so they don't stack, something like...
UNIQUE passive: Why the hell hasn't Riot made a +25% bonus HP item yet?: You ignore a percentage of the target's resistance, encouraging them to build heavy HP items that don't actually exist.
Rebonack2 votesOkay, I guess this needs repeating since most people just aren't aware of how the game's mechanics math out.
In order to get optimum effective HP (as in, the most EHP possible for a given cost) you want to have 1500 HP for every 100 resist you have. If someone has %Pen items and masteries, that number jumps up to 2400 HP per 100 resist. If Riot made it so Void/Whisper ignored 50% of the target's bonus resist, that number would jump up to well over 3000 HP per 100 resist. In such a case your best bet would literally be to just build Ninja Tabi and spam HP items.
The game doesn't need better armor items. Getting 200 armor is trivial. Getting 200 magic resist is annoying, but still possible for people who aren't Garen, Leona, or Rammus. Getting 4800 HP is nearly impossible.
Warmog's has been cemented as the game super-regen item. It should keep that identity. We need an item that can function as a counter-build to %Pen and a +25% bonus HP item would do that without making it a super cost-effective buy on champions who want to just nab one defensive item and then roll with pure offense. Because I can assure you, if Warmog's got bumped back to 1.2k HP it would just become the go-to defensive item on everyone.
Sozan51 votesI don't think we need a %bonus HP item.
We need a normal tank itemization, with top-tier defensive items and some health items.
For example, Warmog could be looking like this: Cost: 3560 Health: +1200 Passive remains the same.
The cost efficiency from health would increase from 85% to 89%, so I don't think it would be game breaking buff.
Some other items that would give high health and low armor/mr would also be good, like:
Cost: 2900 Health +800 Armor +35 UNIQUE Passive: Each time you are hit by basic attack or single target spell your movement speed increases by 5%. This effect stacks up to 3 times.
Or they could just change the %penetration to apply only to bonus armor and magic resist (so that champions would lose damage against squishy champions if they decide to build LW and VS - making it more of a choice, rather than a must-have item thus helping tanks a little bit).
Fertsa1 votesThere used to be a +25% bonus hp item, it was called spirit of the ancient golem. it was used in a cheese build to get dr. mundo over 10k hp.
Bodkins Odds1 votesUNIQUE passive: Why the hell hasn't Riot made a +25% bonus HP item yet?: You ignore a percentage of the target's resistance, encouraging them to build heavy HP items that don't actually exist.
Why not just lower Warmog's base HP to 640 then give it a unique +25% bonus HP passive? That would give you exactly 800 HP if you have no other sources of bonus HP, so the price wouldn't even need to change that much. It's already the go-to HP item, so I think it fits.
Warmog's Armor: +640 health Unique Passive: You gain 25% extra bonus health. Unique Passive: You gain health regeneration equal to 1% of your maximum health. Health restore increases to 3% of maximum health if damage hasn't been taken within 8 seconds.
Cost: 2500G (300G)