Id love if frost had more slows, freezes, and other miscellaneous slows like heartstop aura. Frost fever is just a boring dot, but what about having it build up an heavy slow, and maybe giving it conditions for a root/stun or slowing casting speed? Frost strike? Give it a slow. Have obliterate have a shatter effect. Make pillar of frost actually be a massive pillar where everything in a large radius is slowed or rooted. Remorseless winter could slow targets and make you immune to slows and roots, so it really is remorseless. Heartstop aura for frost only baseline would be pretty sick. Imagine being able to force an iceblock on an enemy you dont want to deal with.
Id like to think that the class fantasy of frost dk is that you dont let the enemy run away, so they basically have to stay with you and fight. It would be cool to literally slow down someone elses gameplay with stuff like slowing down casting/attack speeds and movement. Unrelenting and straightfoward frost vs bursty dot based unholy dk. Without changing a whole lot about how the spec is now, theres plenty of ways that frost could actually be pretty frosty.