When the talent changes hit Live servers I thought the same way about Cauterize... it seemed like a no-brainer.
But in practice what I found was that is is ineffective for the mechanics that killed the most - Infest, Valk drops, runaway Defile, Unbound Plague, even Bone Spike or Blood Beast / LDW melee swings. Since Cauterize doesn't clear your debuffs or threat, you simply just take another lethal tick of the dot or another 1-shot melee hit.
I found it to only be situationally useful for a limited number of things... most notable cheesing Pungent Blight. But even there I was already used to ignoring all spores and /cast Ice Block followed by /cancelaura Ice Block after the cast completes. Cauterize saves maybe a GCD or two at most there.
I haven't had the good fortune of playing in beta, so are there really opportunities for Cauterize to shine now? I was very disappointed with the ability in ICC, but would love to give it another chance if there is good reason to.
I think you're missing the key point that Vontre made, which is that it's amazing for progression content. Obviously when you're using it on year-old farm content in ICC, you shouldn't be messing up enough to make it useful. But on progression, being able to have one mistake a minute covered is a pretty big deal. And yeah, Cauterize may only save you for a split second from a mechanic before it just finishes you off again anyway, but how many times have you needed to Ice Block during your GCD and ended up dying as a result? That second or two that Cauterize gives you is potentially huge.