Cool, I actually made a similar excel file last weekend. I'll also post it here for a download, although I plan to make extensive changes in the future to make it more convenient and useful. I'll probably upload it somewhere permanent when it's in better shape.
The important values here are really in the ratio column, which tells you, based on your current stats, the value in life of each point in armor, each point in resistances, and each percentage of DR from equipment. That should let you make some trade-off decisions when you're comparing equipment. Otherwise, the comments in the excel file should explain the rest.
Resist X is tricky it depends on what damage types your being hit with how effective it is, you got the maximum effectiveness of it, if its the major damage type it far more effective than anything else and is on a par with resist all.
And as such the sheet assigns EHP per point for individual resists to be 1/6th that of "all resist". If you're trying to raise all resists equally across the board, it's a good way to measure things. But yes, obviously they are situational - there's only one generic case and that's improving all resists through these individual +resist mods.
block is even more difficult to assign an EH value to than regen effects.
Case 1: Fire chains/electrified champion pack. Each time you "block" a tick of the fire chains or one of the charged bolts, 100% mitigation. If your shield has 27% block, that's 27% DR. From a value standpoint it's identical to being surrounded by a big group of weak trash mobs.
Case 2: Say that same champion pack is one of the big hulk/demons in act 4 that pounces from the sky smashing a mace on your head. Each melee hit you take is huge compared to your shield's block rating. If your shield has 27% block, you might be getting 3% DR.
Block is so subjective that I can't put an EHP number to it. I could include an "adjusted block amount" on the sheet, though, based on mitigation. This would be an interesting thing to know.
I was looking at optimal gearing last night in a4-tier inferno gear, and with optimal rolls on defensive mods a wizard can achieve 95% mitigation with over 1 million EHP. With a Sacred Shield's block value of 4700, that's a 94k absorb per block. Now obviously that's with OPTIMAL gear - but gear with good affixes and less-than-perfect rolls can still get you close to that. The story gets more interesting for monks and barbs, who get additional defense bonuses. These guys could feasibly see a max mitigation around 97%. There has also been some talk about witch doctors and their additional sources of mitigation, but I don't know how that works or whether it'll be manageable.
Block is horrible the best you can do is this damage blocked = block chance * block amount. Due to the fact that it unlike every other damage reduction in existence is flat.
This means that it effectiveness is say 10% damage reduction vs mob is dependent on the mobs damage double the damage dealt you halve the EHP boost the shield gives.
I think the easiest way to include it will be to treat it as a %heal when hit.
^ As for Skills they are an extra %damage reduction that it look like stacks with the rest in the same way.
IE a 25% damage reduction from skills = +25% more effective health (and a 25% boost to effectiveness of all other damage reductions per point).