Before you had the choice between these two. because Sunfire gave more Health and an aoe while randuins gave more armor and atk spd slow. but now sunfire gives less Health than Randuins AND less armor. sure its a little cheaper but didn't riot mention that they were never going to change or make an item a "weaker"variant of an item(believe the topic at that time was Last whisper and making BC just another weaker LW) Now it was do i want more hp or more armor,to decide your choice. now there is no choice. Randuins is better in almost all ways so sunfire is just a "weaker" randuins.
Randuins > Sunfire
+500 health +450 health
+70 armor +45 armor

Sunfire is an offense/defense item, Randuin's is a utility/defense item.

It's true; Sunfire is like Atmogs; the passive is why you get it. I do agree that Sunfire could stand to be buffed again though; maybe up the damage to 60, or even 80; leave the rest as is.

40dps vs aoe AS debuff.

sunfire needs buff

Since Axes loves his silly "40 DPS is a lot" calculation, here's the actual numbers for anyone else to achieve 40 DPS:

Base attack speed of .625. In order to reach 1.0 attacks per second (meaning you deal your AD as DPS), you need 60% bonus attack speed. For most champions, that is achieved from basic level ups. After this point, every point of AD increases your DPS by a parallel amount.

If you have practically ANY attack speed item giving 40% or more, you'll be dealing 125% of your AD as DPS. This puts Pickaxe (875 gold I believe) at 31.25 DPS. You don't have to buy anything else to get there, you just buy Pickaxe.

If you buy a Cloak of Agility (15% Critical Chance), you increase your DPS by 15% of your PREVIOUS calculation (not the base calculation.) This means that, with 100% increased attack speed, you deal 1.25 * 1.15 * your AD as DPS. Pickaxe does 36 DPS.

So with two VERY minor attack speed and critical chance increases, you can get your AD to DPS efficiency nearly to the level of Sunfire Cape, and the AD to DPS conversion has a lot better (and more) scaling functions to utilize, unlike Sunfire Cape which has, literally, only Magic Penetration.

So, yes, Sunfire Cape isn't bad. Early game. Once you get past a certain point, though, it is less efficient than practically any other stat. (Heck, I believe, with the scalings, even Atma's Impaler provides a better DPS efficiency, and it has even ANOTHER scaling function.)

your comparing 2 items that give totally different utilities, one provides AOE damage, not single target damage which is what most people are showing in calculations. the other provides debuffing in the form of slow in attack speed and movement

if your constantly being the focus of everyone's attack and the damage is mostly coming from auto attack damage, then omen's is a clear choice to pick.

if your looking to provide a little aoe damage, your ability to farm is poor then sunfire will provide that for you

also aoe damage cant be calculated since the amount of damage you do scales with the amount of people are in the area. so 40 damage to EVERYONE within your area is a lot of damage. against 1 person though its not much.

you gotta buy items based on what situation you are in and what you need, not just based on the flat stats it provides, if thats the only thing you are looking at then you arent looking at the whole item

I'd say 40 dps is good, but a lot of people have a health past 1000 and due to MR it'll only do a third of that amount at most. Unless you are grabing a good chunk of MR Penetration.