Updates:

Item 1
I worked out what the spear deal bonus damage to; Spectators. It feels restrictive to only have it affect that one type of creature, still think having it affect spiders and other animals with more than 1-2 eyes makes sense too.


Item 6: Legendary Staff
The staff you get from combining the 3 icy items in the Underdark seems very underwhelming for being "legendary" maybe it's just because it's an Act 1 legendary.
The way that Frostbite works is it adds 1*duration cold damage to your attack when you inflict cold damage, however because it only lasts one turn you can't gain the benefit of this effect yourself. You need to have another spellcaster in the group to use a cold spell after you apply the debuff.
The duration needs to be increased to allow you to self-proc the extra damage, a 2 turn duration would be fine allowing you to proc the bonus damage on your next turn. As it's possible to have this effect up permanently on one target a duration longer than 2 turns with it's current 1*duration bonus would be way too strong.

[Linked Image from i.imgur.com]