To get the equivalent melee reduction from a belt using only armor and resists you would need 550 armor and 131 resist,
I was aware that my choice of words (protection) could be misinterpreted, I was speaking in terms of EHP (ie including vit). In terms of protection, ie DR, a good SoE is a very good belt indeed. The choice between EHP or DR has all sorts of implications when trying to model specific instances such as Diablo Inferno, where going for either can be the best choice to increase survivability, as block has exponential returns for increasing DR.
If you take a close to perfect SoE with very strong random properties it is going to be the best belt yes, however you could argue it still isn't worth the gold. I'm comparing a ~120 str + 120 vit 20@ 20 dr (with a 50 million pricetag) to a 1 million belt currently on the auction house with 160 vit 40@ 60 phys 100 strength, and having my character around 10k armor + 900 phys res the SoE is indeed better by around 9% in terms of ehp. However, the cost is also 50 times higher, or ~5,5 million gold / %ehp.
So yes, extremely good rolled SoE with the perfect random properties are the best belts, but also expect to overpay by ridiculous amounts.
For comparison's sake, the best SoE for 1 million gold I could find is a 300 armor 54 vit 15@ 10 dr with rest random stats, and I'm presuming I don't even need to tell you that you barely have to spend half of that to surpass it with a huge margin. For example, my current belt is a 140 vit, 286 armor, 63 int, 30@ 43 phys res, and I'm seeing an EHP increase of ~20%, for a third of the price.
The reason I said SoE is bad isn't because of its inherent potential to be the best belt in the game (which it can be, as you say), but most people don't have an infinite amount of gold to spend on such a gosu item. If you're spending far and away beyond 10 million gold, then yes, you'll be beating the rare belts. By a huge margin? No.
If you're looking for value for gold, SoE simply isn't a good choice in any scenario (unless someone accidentally drops it on the AH way underpriced by orders of magnitude), as you have to spend about 5 times the gold to surpass the rare belts for any given level of SoE.
Here's a belt I bought for 1.5 million (comparable price to a good string)
After owning and using both, I personally think it destroys string... Only a 20/20 string could come close I feel. Which is ridiculously expensive.
I don't know how "key" these items are because they are far from cheap and the first one is a very lucky roll but I was lucky enough to find and IK's Will helm with 45 all res. If I couple that with an IK's Soul Cage chest piece (around 60 ar iirc?) and then you add the 2 part bonus of an additional 60 resists that will net you a total of around 165 ar. Add impunity into the mix and you're looking at just under 250 ar from 2 items, which shouldn't be sniffed at.
I would say use the IK belt instead of the helm with a lucky roll as it defaults with resists but that would obviously remove the SoE.
Yeah that's what I thought. So it would be more effective to try to go for a low hp and high res/armor build if you go for high block rate.
Except you can only get your block chance so high, and at realistic block chances vitality is still quite strong, so you need to be careful here. Monster damage is hard to predict. You're going to fully block attacks too, and when you fully block attacks the effect you're talking about doesn't exist.
As for strings, I snagged a 20% one real cheap, but all this discussion got me thinking about selling it for several millions and buy a 1-2 million belt... Does a 20% string (without other stats) really sell that high? My guess would have been 2-4mil, and at that sum it's not too easy to compete by trying to buy a rare belt (at least from the limited searches I've done), at least not without getting a lucky find.
Note that wrath of the berserker can help with enrage timers, but if you're hitting them without being even close to killing the monsters it's simply not going to be enough.