Resistance gear entered my mind again for TBC after a humbling encounter with Steam Surgers in Heroic Steamvault. Some frost resist for those mobs would certainly come in handy.

I thought of Void Spheres: the +4 resist all socket gems. But would those cut it? Realistically, if I duplicated my gear, I could fill 15 to 19 sockets in total. That's only 60 to 76 resistance overall, which is still "poor" in the character pane, but it's sure nice to have one set for all schools of magic rather than multiples overflowing my bags. Plus, it'd be pretty awesome DPS for resistance gear. I could augment with rings, necklaces and offhands for a possible total of 169 resistance.

169 is a far cry from the max of ~370 resistance (see WoWWiki), but the max is based on level 73 mobs ala "??" raid bosses. For Heroics, where bosses are level 72, it may be more realistic.

Theorycraft can only go so far and real-world (or at least game-world, lol) results are more fun to obtain. =)

Without investing in expensive Void Spheres yet (35g each on my server's AH), I collected a set "of Shadow Protection" greens at cheap prices. I kept the resistance modest from my goal and tested with 151 Shadow Resist total. The mobs for my test were Wrath Corruptors @ Forge Camp Wrath in Blade's Edge (near Ogri'la). They spawn randomly between levels 70 to 72 and spam Shadow Bolts.

My results? After being hit with 200 Shadow Bolts, I resisted 36% (38% if full resists are accounted for) of the overall damage via partial resists. Much better damage mitigation than I thought it would be.

I'm going to start collecting a duplicate set of socket gear and fill them with Void Spheres. Once I've obtained my dream resistance set, I'll post results from actual Heroic runs.