I've wondered about this for a while, and finally decided to ask about it. I've seen high-end raiding guild melee with Icy Enchants on their (obviously) primary weapons, ie a Perdition's Blade or Quel'serrar. Does Icy have an important use on some raid bosses? Does it have a snare effect that works on them, or a melee slow effect?
Hmm, I honestly don't know -- I assume it doesn't stack with most slows, just overwrites weaker ones like Thunderclap? I know that back when we did MC and such a year ago, Icy was popular because of the melee slow effect (yes, it works on everything). The problem is that it's a low proc rate, so to keep it on all the time, you need a lot of melee with it. That's a lot of collective damage to be giving up.
And once you have a Thunderfury, you have a permanent -20% anyway.
We used to have a lot of rogues use it on their offhand and it was pretty nice. Then they introduced the +15 agi enchant and then it was just on a few tank weapons.
You really do have to have a lot of people with it to get much use out of it due to the low low proc rate.
I'm curious to see what if any melee slow affects stack with each other. I know they changed thunderfury to not stack with other thunderfuries, and to not stack with thunderclap, but I wouldn't be entirely surprised if they forgot icy chill.