User blog comment:Lukeatlook/Pyro's Item Overhaul 7 - The Tank Project/@comment-8468980-20141221193529/@comment-8468980-20141224031152

"The idea is to not just remove the active, but also rip 20% of base stats from Omen. 100 less health and 20 less armor is enough to take a second look at it."

Remember that armor (and even HP) get diminishing returns the more you stack it. 20 less armor and 100 less hp is nothing compared to granting them a unique mitigation mechanic that force multiplies their stats.

"In melee combat and against mages this is straight out worse defense."

100 less hp isn't somehow going to make them far more vulnerable to mages, in addition it's not a strong argument to begin with since players aren't going to buy Randuin's to deal with mages, that's really just a fringe benefit to current Randuin's. Against melee ADCs (all 3-4 of them) it just may be a nerf, but you really aren't giving LoL's block mechanic much credit. There are reasons why Doran's Shield has the only unique passive amongst doran items, and why S2 block masteries got nerfed so hard. Not only is it powerful because it force multiplies other mitigation stats (instead of having dimishing returns) it also allows the bearer to become virtually immune to creep waves. Top laners will be able to freeze lanes anywhere they please with no repercussion.

"It makes for a soft taunt - hit the Sunfire wielder and the damage will get lower."

A support tank's threat doesn't come from changing aoe damage from 40 to 20, it comes from limiting its ability to initiate or peel. This is in no way a soft taunt. The actual numbers sunfire produces in your suggestion will nerf it's ability to deal damage after  focus fire against whatever tanky target is wearing it, but if they're getting chunked in the first place they aren't relying on that damage in first place. The reason why Riot nerfed Sunfire the way they did at the begining of S4 is because it was overbearing for Dr. Mundo, Shyvana, Renekton, Trundle or Darius to rush this item, push their lane easily because of it's high aoe at low levels, and then roam mid and deal high aoe damage to their enemy mid laner since it's still early-mid game. In its current form, I think it's perfectly fine.