I have seen both Frost damage and Cold damage modifiers on separate items but just now I had a chest piece drop that gave a Frost damage modifier and a Cold damage modifier both on it.
AFAIK, Cold damage is general and Frost damage is Sorceress skill specific. The damage should be in the same bucket (additive) so doesn’t matter which one you get.
There is no “frost damage”, but there is “frost skill damage”.
“Cold” is just a general damage type, “frost” is a category of several sorc skills.
Most (if not all, though I’m not sure about Shatter, even if it’s damage is not increased by any bonuses) offensive frost skills do cold damage.
Ice Spikes from aspects do cold damage (at least tooltip for aspect of frozen tundra says so), but they are most likely not frost skills and so do not benefit from +frost skill dmg bonus.
thats not true unfortunately. at least there is a nm dungeon buff that says 15% more frost damage. its not saying 15% more frost skill damage. me playing ice spikes blizzard is wondering if this buff even applies to the ice spikes