Idea shield would be overupped tirifing carded shield. Tirifing reduces damage from medium size monsters, while khalitz reduces damage form demon property attacks. So Khalitz is pretty much useless in niff, except against that one attack that Dullies do.
As for armor, yes holy robe is actually quite efficent in Niff, if you can get an overupped holy robe then that's probably your best bet. As for alternative, an overupped Garm saint's robe is also good. Some people prefer to use Diguise armor as well to prevent any monster skills. And some use shadow/undead (Bathory or evil druid card) property armor to decrease the damage from that shadow attack dullies do.
But Tirifing shield and overupped Holy robe are probably the best in my opinion.