Before we get too excited and start reworking priority rotations to drop CB/SW, there seems to be a fairly constraining set of circumstances in which Devastate is wholly worthwhile to use in place of CB/SW. This is to be expected, as CB/SW scale, much, much more strongly with AP than Devastate does. Let's examine some assumptions quickly:
1) At lower AP levels (say, before 3400 AP, raid buffed), Devastate is almost always better for threat than CB/SW because of the bonus damage it gets from doing weapon damage plus bonus damage based on sunder armor stacks.
2) Devastate needs a lot of support to be sufficiently propped up. Near as I can tell, there are five ways to buff Devastate's threat:
Using a Cudgel of the Damned as a tanking weapon, in addition to getting you kicked in the face by your melee DPS, is not by itself sufficient to boost Devastate above either CB or SW in damage OR threat. Likewise, using the Glyph of Devastate by itself will not boost Devastate above the other two skills while using a lower DPS, faster tanking weapon like the Peacekeeper Blade. All these assumptions are drawn from my personal (meager) Warrior using Wartotem's Spreadsheet. Your mileage will vary.
3) When you reach a certain threshold of AP (eg. you're in a threat oriented gearset with a proc trinket that gives AP, a la Mirror of Truth), CB/SW are going to flat out win no matter what your weapon speed or set bonuses are. Because SW can't be parried, it will take a lower threshold of AP for SW to match Devastate's threat than it would take for CB. For me, using the "best case Devastate scenario" of 2 piece T8, 2 piece T9, Glyph of Devastate, with a Cudgel of the Damned, the threshold was ~6800 AP raid buffed for SW and ~8200 AP raid buffed for CB.
I'm not a big numbers guy, so I'm sure a lot of this is "well duh," information ("Why yes Wyuli, SW DOES scale better than Devastate. Here's a cookie"). I do think it is important, however, to make sure the right conditions are present for dropping CB/SW to be a good idea in an individual's threat rotation (and so we can avoid a lot of, "But I read on Tankspot that using Devastate instead of CB/SW was always a good idea...." discussions).
I support Wyuli's statement. I originally made the spreadsheet to find out exactly where/when those turning points in threat occured and after a lot of fidlling around with it, I can tell you that there is no optimal all-round rotation.
Most of the skills are close enough together to not matter much, but if you really want to max either DPS or TPS, you'll need to find your own rotation depending on your gear & buffs.