So uhh, this is still something that runs me up the wall. The only sources of frost damage I can think of are the Comet morph of Meteor, ice destruction staff spells, an ice damage enchantment, and the iceheart set(aoe damage, unsure if it counts as direct or dot). Other sources require a primary source of ice damage to proc from.
Most obvious is that it's heavy armor. Not necessarily a problem, can still be useful this way. It's more limiting for the healthy trait on the jewelry that comes because of this, but again not that big of a deal. Then we can notice that it still gives magicka, spell critical and
weapon damage. Exactly that kind of change into a concise set that gave magicka or stamina sets made red mountain a popular set.
Outside of "problems" with the set, if I had a little more personal note on it I would have to say that it's just plain really bad. Like, if you get a direct ice attack in twice every second with no failed procs it amounts to 1k aoe dps. That's just pitiful, I really mean it. In my opinion this set just needs an entire overhaul at some point. Here are my recommendations:
Ice Furnace (Heavy, S&B oriented)
(2) - Increase Spell Resistance
(3) - Increase Max Magicka
(4) - Increase Max Stamina
(5) - 25% chance when blocking an attack to emit a chilling cloak for x frost damage every second for 8 seconds. Additionally, this effect's duration can be refreshed by additional blocks doubling the area of effect up to two times (maximum 12m)
Obviously numbers are something I'm not going to perfectly pin down, but the concept of a constant swirling cloak of ice strikes me as awesome. Perhaps slice off the idea of expanding the aoe and instead snap a guaranteed snare in there for non-DK/sorc tanks.
Ice Furnace (Heavy/Light(?), magicka oriented)
(2) - Increase Max Magicka
(3) - Increase Spell Critical
(4) - Increase Frost Damage dealt by 5%
(5) - Applying the Chilled status effect also deals an additional x frost damage per second for the duration.
Spell Damage for Frost damaging effects is increased by x against enemies under the Chilled effect.
Investing in frost damage is fairly unrewarding as-is outside of some peculiar dueling setups in pvp. The sources for it are few, nonexistant within class skill lines even. And after going through all the investment to actually have sources of frost damage, the sets that synergize with it are few and the only intriguing one requires participation in maelstrom arena. Iceheart deals ice damage independent of other sources and I consider it fine as-is.
I would be perfectly happy with either of these, in fact at the mention of one of these being put in the game I'd delete a low level sorc I was toying with to make a build oriented entirely around it. I like frosty themes, and right now there's not much too it in ESO.
EDIT/DISCLAIMER - I know many (all?) sets in ESO come from some inspiring theme in the lore whether old or new, though I couldn't really find the source for the "Ice Furnace" in a casual googling. Maybe there's some reason that it deals fire damage off of ice in an area, or maybe there's not. I would prefer the word 'furnace' wasn't taken to mean it has something to do with fire, and keep it an ice themed set on the whole. That's my personal view, if you like the fire thing just imagine the sets written above deal (partial) fire damage perhaps? ^^
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