It also seems important to note that if you chaincast Snipe you will very quickly go OOE, which is not the case with Disturbance which you can spam for a LONG time before going OOF (or indefinately if you have Concentration). Further, Sages don't need Accuracy so can instead stack Alacrity which brings the cast time down
Anyway, as Kitru mentioned, only TK really uses Disturbance.
Seers will be using Weaken Mind, Mind Crush and TkT before Disturbance. Some will even use Project first but the efficiency there is iffy. So that's 6-7.5s of downtime from healing before they reach Disturbance on the priority list.
Balance Sages will just spam TkT until they need to reapply DoTs or use FiB. Any uses of Disturbance (even with POM procced) just wastes Force and leads to using GCDs for Nobel Sacrifice later.
TK Sages spam Disturbance as a filler and proccing ability. It's below everything (aside from idiotically hard casting TK Wave) on the priority list.
This is all true. This is also my point. For no spec does Disturbance seem to be anything more than a move used grudgingly, and that's just for TK/Lightning. The other two specs just ignore the power altogether. Now if it was awesome for TK spec, that would be different. There are plenty of powers that are pretty much made for one spec or the other. Mind Crush seems like a primarily Balance spec power for example. But Disturbance really isn't much TK other than to proc effects.