It does have a huge TP cost. It's over 100 TP to use it. Not to mention most things become stun resistant, so spamming it doesn't do much.
Besides, DRGs, WARs, and NINs (with one of the poisons) all have stuns that are OGCD and they use them in their rotation because they do a bit of damage. I'd rather avoid having it become one of those skills, I'd just really like not to miss stuns because I was in the middle of a Halone combo and I have basically no skill speed.
