If any of this is inaccurate let me know, none of the data I found on WoWhead/MMODB seems reliable...
Resistance effects and values @ 85:
Mage Armor: 45 (confirm?)
Mark of the Wild (Druid): 136
Blessing of Kings (Paladin): 136
Elemental Resist Totem (does not affect shadow) (Shaman): 195
Shadow Protection (Priest): 195
Resistance Aura (Paladin): 195
There are also racial (Undead, Draenei, Worgen etc.) effects that now give +85 Shadow Resist @level 85 instead of -% chance to be hit. Apparently these don't stack with the resist buffs anymore; for example, an Undead with Shadow Protection will still only have 195 Shadow Resist instead of 280. So extra pen/hit won't be necessary for these anymore.
Spell hit: 4%, racial penalties are gone and so is the +hit talent we used to have in 3.0, so with 102.5 hit rating for 1% spell hit at 85 (that's the value I found at EJ), you should be aiming for 410 hit rating unless all your friends are Draenei.
Curse of elements reduces resistances by 183 at 85, so you can basically rely on keeping that up for the majority of Spell Penetration needs, but with the buggy way Jinx works and the value of the utility curses (CoEx/CoW/CoT) I think I will prefer gemming the Spell Pen on my gear for the time being. If you'd prefer to rely on CoE alone, read no further. Also, I think the Mage Armor bonus is now minor enough that the main goal should just be 195.