I'm really seeing a lot of potential in frost, I was able to get some relics for the swords to bring it up to 890 (remember this is/was OS), I cleared Heroic with my guild and did some Mythic as well as Mythic+ content and it felt extremely satisfying to say the least, I feel confident with a frost legendary or two and the incoming buffs next reset that it will overpower unholy by a good margin!
Frost does however feel EXTREMELY squishy compared to unholy, where I've gotten used to popping an IBF or a Meatshield in case of emergency I no longer have these abilities available to save me