Cold sorcs can lower resist to minus 100, because good ones can have near -250 enemy resist on their attacks. If you have 70 from fade maxed +30 from anya + 30 from maras, that's 30 resist in hell, anni = 50 resists in hell + shako um = 65 resists in hell, the only ways of beating a cold sorc imo is to either go out pure offensive where you try to kill them with as little resist gear on as possible as it won't make a difference, you'll be -100 resist anyway; or you can have defencive gear on, where you kill slower, but live longer. I have many pieces of gear for my assa in my stash, i use 1 set for most people, but it changes depending who i go against:
bramble for most fights as it adds insane amounts of damage, and people do damage themselves quite a bit when they attack your shadow master.
coh dusk for when i need high resists (cold or sometimes foh)
many resist charms (6x 11% lightning resist and 6 x 11% cold resist), you lose damage and life, but it's better than dying so quick. at level 80 my ww assa works pretty well and beats most other people:
caster setup i most normally use i have:
3k life
6.8-8.2k ww combined roughly, works very nicely
58% claw block
max 50% dr
max resists apart from lightning in hell with fade.
only 7k ww ar for casters, 16k with angelic and haven't tried demons limb.
This is from rebuilding my assa and staying much closer to Xu-God's build. I'll level this beast to lvl 85+ this weekend hopefully