Trang's Belt could be replaced with Credendum of the Disciple set, which has +15 resistance, as the synergy for Trang's +40 Cold needs 3 items. Your Boots should either be Aldur's or high Natalya's. Armor should be Enigma, or Chains of Honor, if your resistance REALLY need the kick.

Generally, Summoners should use Enigma, just so you dont lose anything, but Summoners usually don't ever get hit. Ditch the Bramble, as Thorns can be provided by a little friend I like to call, an Act II mercenary, more specifically, Combat Nightmare.

Your merc could wear it instead, and you can opt for a Might/Defiance mercenary, but you sacrifice Fortitude. Then you can make a Doom, which has Holy Freeze, Pride, which has Concentrate, Hand of Justice has Holy Fire, Infinity (LOL YEAH RIGHT).

Can't use Last Wish because of Beast, but that may be covered by mercenary. Dragon can be worn, if you lack a Holy Fire.

I'll finish this up later after a response or further research.