What does your cold resistance say right now? If it is under 75% then you won't notice a difference.
I think you are getting confused between
maximum resistance and resistance in general. Hard points into the paladin resistance aura skills will increase maximum resistance only, they won't give resistance itself but instead increase your potential maximum resistance cap.
Perhaps an example would help.
Character, in Normal difficulty, wearing:
Skin of the Vipermagi (30% resistance to all)
Laying of Hands (50% fire resistance)
Now that is 80% resistance to fire and 30% to all other elements. Your maximum resistance to any element is 75%, so at this point your fire resistance is actually only 75%.
Now if you place two points into the Resist Fire skill your maximum resistance to fire is now 76%, so your total resistance is 76% to fire. To take it a step further:
Code:
Hard points | Fire resistance
2 76
4 77
6 78
8 79
10 80
12 80
14 80
16 80
18 80
20 80
You'll notice that fire resistance tops out at 80%, since that is all the equipment you are wearing allows for. However at 20 hard points your
maximum fire resistance is 85%, so if you put on equipment worth 5% more fire resistance you would reach that value.