One of the passive abilities available to the Wizard class is called glass cannon. It does the sort of thing you'd think a passive with that name would do... You deal 15% more damage and lose 10% of your armor and resistances. 15% damage is a lot of extra damage so I took this ability as soon as it was available and kept it for quite a long time. My theory was that I was probably dead if the enemy got to me anyway so I should just do more damage while Tom's dogs tanked everything.
Eventually the dogs became so bad Tom stopped using them. Our strategy for dealing with powerful elite packs morphed from burn them out to a combination of kiting and graveyard zerging them down. Guaranteeing that I never got hit was no longer plausible. I could no longer afford to die in one hit! So I geared up some extra maximum health, I dropped glass cannon, and I started using diamond skin. It's been working out pretty well so far.
This morning we ran into Hell Belial and he's really hard. We kept dying in phase two and eventually decided to go to bed and try again tomorrow. Maybe with some extra gear from the AH. I feel like I'm both not doing enough damage and dying too fast. Should I be trying to swap out more int gems for vit gems? That'll just slow down how fast the adds die. But where else can I get tougher? I was thinking maybe I could switch back to glass cannon to mitigate that switch. Depending on just how bad losing 10% of my armor/resistances ends up being anyway...
The first interesting thing to note is armor reduces all damage done. Getting hit with a fireball? Armor will mitigate that damage. The second interesting thing is that there's a physical resistance stat. There are resist stats for all damage types. The third interesting thing is that both types of damage reduction apply to all incoming damage, multiplicatively. As far as I can tell, the percentage damage I'd take right now (as a level 56 against a level 56) is:
And with glass cannon:
With my current values this results in an overall increase in damage taken of 6.05%. Because the two are multiplied together the cost of glass cannon actually goes up as you get better gear. I have almost 20k health right now so I can maintain my current survivability by adding an extra 1210 health and picking up glass cannon. I'm getting 31 health per vitality so I'd need to find a mere 40 vitality to break even. That's pretty much one socket switch! Losing 40 int would cost me a little less than 5% of my damage and glass cannon would be 15% extra damage so it actually seems like a pretty reasonable option.
The only downside is it costs me a passive slot. Right now I'm running 15% cooldown reduction, 20% melee damage reduction, and a massive boost to my arcane power. I think the arcane power boost is mandatory with the way I play. The cooldown reduction is really important for Belial in particular since I feel like I need to cast frost nova and diamond skin as often as possible. And with all the damage the adds do being melee damage it actually seems that the 20% melee reduction is better than glass cannon. On other fights I could totally see it being a reasonable swap, but probably not this one.