It's because, if you're a healer in Warsong Gulch or Twin Peaks, an enemy Druid can keep you locked out for long periods of time while his friends turn your FC into mush.

Go play some higher-rated arena matches and tell me if you feel the same way. Cyclone is an amazing CC; five seconds where you can't do anything, whatsoever, to help your team. Sure, you can't be hurt or CC'd further, but does that matter? If you're being Cycloned, it's not because you're being focused, it's because you could help a partner or disrupt the enemy team's flow. Being forced to wait five, painstaking seconds before you're probably CC'd again (and yes, it happens often) is awful. For an enemy team, it's a great opportunity to land a kill. You shouldn't pop out of it because odds are, there's an even worse CC coming at you (Blind, i'm looking at you), so you're typically forced to wait it out. Even if you do pop, within the next thirty seconds you'll probably be wrapped up in that tornado again. The amount of pressure Cyclone puts out is immense, which, for me personally, places it on my "most reviled" list of CCs.

From a 2.1k experienced Resto Shaman's perspective

I think you're crazy, Kendro. For every other CC, I typically have a few options. With Cyclone I'm just out of play completely unless my trinket is up, and then I'll just be cycloned again as soon as I use it. It's a devastating cc.

This is where I love one of TOR's ideas, that CC immunity bar of theirs. In a nutshell, Bioware made a single diminishing returns affect every CC in the game, and added a graphical representation of how much diminishing returns on CC has stacked.

What this means is that CC-locking a player is impossible, because before long he becomes almost immune to CC and new attempts at CC will only serve to recharge his immunity bar. Also, the player can make informed decisions on whether or not to use CC-breaking skills based on how immune he is to CC.