See, that's changing terms around, because all the sources you get (the DG Database, this guide, etc.) use effective HP as a term for 100% damage mitigation by armor, which is the edge case (and why such calculators aren't very useful.) If you do the math for a % of damage mitigated by armor, its obviously more relevant.

Well, here's a question.

Would you rather have 2500hp and 50% mitigation, or 5000hp and 0% mitigation?

Against a demigod who relies solely on physical damage, the life expectancies of both of these characters will be the same.

Now think about the 2500hp/50% mitigation guy. Sure, he will live just as long against a physical demigod, but armor does not mitigate spell damage, so against a Torchbearer he's screwed.

But there is also a disadvantage for the high hp guy: if you have low armor, you're losing health more quickly, which means it will take more heals to fill up your hp bar. Your downtime will be a lot longer.

Re: dodge. It makes you avoid a hit that you would otherwise have taken. Therefore, the logic that follows from this is that if the said hit is larger (i.e. you have low armor), then dodge will be more valuable. It is not a big deal if the hits you are dodging would have done 50dmg to you, vs. 300dmg.

lukkas, thanks for putting together the data for your original post.  Very valuable stuff!

After reading this thread, it seems some people are caught in a false dichotomy of HP>armor or effectiveHP>HP.  As Lieu has pointed out, damage mitigation via armor is something that's important to be aware of.  Milskidasith, as you point out, spell and ability damage completely bypass armor.  While this is obvious to many of the more experienced players, it's good to spell it out for the newcomers to the game.  The more nuanced players understand that armor is more important in some matchups than others.

The matchups where I tend to armor up in are usually when I'm playing a melee DG against Rook, Oak or UB or Regulus.  As an example, if I'm playing as Sedna and I see that an opponent Rook is tower spamming and using arrow shoulder turrets, I'll usually pick up +HP and +Armor.  If my armor mitigation is around 50% I'll be more apt to chase Rook into his tower farm and pounce/melee him to death.  If I don't have armor, I'll most likely be running away to a different part of the map.  And if there is an enemy Regulus on the field that has been sniping, I'll be very careful to never let my raw HP drop below 1500 or so.  As Sedna relies on close range attacks, I expect to get hit by towers and DG autoattacks fairly often... so I usually get armor.  The percentage of hp to armor really depends on my role for that match.  If I'm pushing a lane and clearing towers, obviously I get more armor.  If I'm primarily healing and capping flags, I'll go for HP and speed and remind myself not to get too close to towers or UB/Oak/Rook/Minions.

On the other hand, if I'm playing an offensive support role with, say, Regulus, I almost never get +armor items and instead focus on pure HP, HP regen, mana and speed.  The reason being is that I'm primarily sniping with Regulus or laying mines, and I don't get hit much by minions, creeps or towers.  I really only need to worry about TB fireball, enemy Regulus snipe, UB poison, Oak penitence etc.  I know that sometimes I'll be hit by autoattacks and towers, but I'll say less than 10% of the damage I take in a given match as a sniper will be non-DG damage.  So I'll grab some +HP gear then put the majority of my gold into the citadel as the game goes on.

The trick is to be aware of how armor mitigation works and use that knowledge to blend in your item purchasing strategy to best serve the tactical requirements for the given match.  And anybody who's read this far into the thread has already improved said awareness, so thanks again lukkas as well as everybody who contributed to this thread!

I absolutely agree.