Honestly I don't know if this trinket is as awesome as it looks. I'm afraid not, at least not for raiding purposes. Although this picture of an army of tiny gnomes, taking down Illidian, which I found on the WoW forums, tells quite a different story.
The damage isn't really too impressive. The gnomes makes some kind of sparkles which hurt for 150-200 dmg each for a short while. And then there's 10 minutes of cooldown, so you can't use it that often.
I've been told it could be useful in PvP though, so I'd better try it out. If nothing else - just to confuse the enemies a bit by all those gnomes running around. And I'll definitely use it in duels, just to give myself and my guildies a laugh. Which is epic enough in my eyes.