So after trying to figure out why I am such a trash can rogue pulling sub par dps I analyzed all the top rogue parses from the raids. None of the combat spec rogues doing great dps use rupture at all. That should be removed from the rotation in this guide.
I'm not sure if that qualifies as a terrible post, but here's a reply anyway.
If you are looking at Stone Guard parses, that is a blade flurry fight and you don't use rupture, since it doesn't benefit from bf. I looked at the top few combat parses in WoL on the next 3 fights and they almost all used rupture (10 out of 12), ranging from 30% to 75% up-time.
And even if nobody was using it, it doesn't change the fact that if used optimally, it is a small dps increase.
That said, if I sim my rogue, adding rupture to a rupture-less rotation increases the dps by only 1.2%. So if it's simpler and easier for you to just use eviscerate, you are not losing much from the theoretical max (and it may actually help you a little, if trying to keep up with rupture was distracting you from doing other things properly)