My guild has had no luck with Thunderfury so we are thinking about crafting one of these.
http://www.thottbot.com/?i=23922

Before we blow a ton of mats, can anyone answer
-Does it work against bosses?
-What is the proc rate?
-Who should wield it (MH sword)?

and basically
-Is it worth the trouble?

Any input would be appreciated. Thanks.

Forgive me if i'm wrong, but isn't the proc the exact same thing as the icy chill enchant?

pretty much - and icy chill is awful. It'll knock off thunderclap/thunderfury, then stay up for a couple seconds, then go away. And if you can't rely on thunderclap being up for the duration, constantly having to watch buff lists and reapply it takes a big toll on your DPS. No one should have icy chill on their weapons, and no one should ever use Frostguard imo. The biggest issue with it is that it's a proc, meaning it will hardly ever last its' full duration given current debuff mechanics - but being more potent than thunderclap means it will knock thunderclap off when it's applied

Ideally you should have one warrior thunderclapping (if no one present has thunderfury) and one warrior applying demo shout. A single warrior can handle both some of the time, but on a fight where having both up is vital (i.e maexxna) it's best to break them up to ensure that resists don't screw you

Icy chill isn't awful at all. I thought it was until we tried using it.
When we didn't have thunderfury we were able to keep it up about 60-70% of the time. We ditched it after getting TF and 5 piece TC bonus. Which happened almost exactly the same time.

Yes, don't use icy chill with TF and TC bonus, but without it - its very useful, and the dps lost from the enchants is marginal - you may want the dps at times in naxx, but most guilds facing this decision probably aren't worried about Berserk timers.

On my warrior I have icy enchant on my back up tank weapon, and it's neat when it procs. It's absolutely no substitute for Thunderclap, let alone Thunderury, but if neither of those are available for whatever reason, it's better than nothing.

Definately wouldn't waste my time with a Frostguard, however. Ignoring the proc, the mats aren't worth it to craft. You might as well be using Cho'Rush's blade with icy.

Well from a mitigation stand point the low proc rate and short duration make Icy too unreliable and from a threat generation stand point I'm going to assume Icy does nothing or close to, I use TF because I can expect the proc up most of the time and lots of added threat.

I have always wondered how well frostguard + Icy would work, if at all.