Well...it has been stated that going for ISS is a dps loss...under certain conditions.
I don't think that it should be a general blanket statement that ISS will lead to dps loss for survival. When evaluating a survival rotation that uses ISS, we should consider the following:
A) CoS > SS, so within your rotation, you will have to make up at least [(2xCoS damage) - (2xSS damage)] just to break even.
B) Practicality: I will mention 2 points here.
1) A rotation that requires you to uphold ISS will always be more complicated, therefore more likely to drop DPS due to player error or other complexities with random procs such as LnL.
2) A rotation that requires you to uphold ISS will hold a larger percentage of physical vs elemental damage as compared to a rotation that does not require ISS. This means that Mastery is even less important which makes it easier to reforge into haste -- a rotation that requires ISS will ALWAYS be a rotation that is geared towards a large haste cap. At lower haste caps, refer to A -- you will not have the time and focus to make up for the dps loss of casting two SS over 2 CoS.
Keep an open mind when considering new rotations and strategies for playing this spec -- especially as we approach higher gear levels. In BC, the strategies for playing a hunter changed drastically once you hit a certain level of gear, and I suspect that we may see similar things happening in Cata.
Now, to respond more directly to Wiggeh, I don't think analyzing the opener for your rotation is a good way to do things. While an opener is important and can make a big difference, it will most likely not be the deciding factor in the rotation you choose when it comes to a 7 minute fight (or longer).
So for a normal rotation with: 3/3 pathing, Hunting Party, and ISS you are suggesting...
SS>>SS>>CoS>>AS>>ES>>CoS>>AS>>SS>>SS>>ES>>CoS>>CoS>>CoS>>AS>>ES
vs
CoS>>CoS>>CoS>>ES x3
So...
4xSS + 5xCoS + 3xAS + 3xES (/w roughly 1000 points dedicated to haste instead of crit or mastery)
vs
9xCoS + 3xES (/w roughly 1000 points more divided in some fashion into crit or mastery)
So the question is, will 3xAS make up for the dps loss in 4xAS AND the overall reduction in damage due to having lower mastery and crit?
Seems like it might, at best, come pretty close to a tie...which in my mind would make the added complexity of maintaining ISS devalue this type of rotation. I would favor the simpler rotation that pulls comparable dps so as to maintain consistency in my dps from fight to fight.
So...I'm not trying to contradict myself here. What about the next step up in haste caps? When CoS and SS reach a cast time of 1.25s.
Now we have...
SS>>SS>>CoS>>CoS>>ES>>CoS>>CoS>>SS>>SS>>ES>>CoS>>CoS>>CoS>>CoS>>ES
vs
CoS>>CoS>>CoS>>ES x3
or...
4xSS + 8xCoS + 3xES (With roughly 2000 points dedicated to haste instead of crit or mastery)
vs
9xCoS + 3xES (With roughtly 2000 points dedicated to crit or mastery vs haste)
Again, I understand that this will not be accomplished until later gear levels...that's why it's theory crafting. Trading 1xCoS for 4xSS is a pretty good deal. Throwing down those extra SS, again, makes crit more important than mastery making it easier to reforge Mastery into haste without huge DPS losses. Maybe someone can sim this out, I really haven't played with the sim much...I suppose it's something I should take the time to learn.
I do prefer to just come up with stuff for other people to test though.
edit: Oh yeah, I should note... the above rotation at 1.25s casting time generates a HUGE amount of focus in both SS and CoS, but also in the fact that the rotation itself requires a lot of haste...therefore entails a large amount of FPS.
The rotation as presented may not be viable simply because there are not many ways to effectively burn off that focus without dropping ISS or losing dps by dropping CoS in order to get off instant casts such as AS or BA. It is because of this that I can easily envision a point at which, because of gear, there is a spec swapping point where you can dps better with MM or BM than you can with Surv. I believe Surv is highly limited by that 6s CD on explosive shot, but we don't have the gear to do better with MM at the moment. This was a similar story in BC, for those of you who remember.