Snipers (and all agents really) will probably use a priority list rather than a sequence really for all agents due to their rotation being very resource dependent. The priority list depends a bit on the situation and what you actually prioritize on:
DPS - Damage per Second - This ranks abilities purely on what does the most damage in the shortest period of time. This is mostly interresting for short term encounters or for encounters where you have a small window in which you can do (extra) damage*; in this case dots are ranked lowest, after all they only do a few damage every few seconds (*assuming dot's for example stop doing (extra) damage when the window expires)
DPCT - Damage per Casttime - This ranks abilities on what does the most damage per cast time. This is almost the same as DPS with the difference that for damage over time abilities the full damage is counted. So if a DoT does 3000 damage over 8 seconds with a 2 second cast its DPS is 300; but its DPCT is 1500. DPCT is identical to DPS for abilties that do all their damage in 1 bit (like most of our shots).
DPE - Damage per Energy - This is probably the most interresting for us, as agents seem to mostly be limited by energy (keeping it above 60). Basically you divide the damage by its energy cost and base your priority on this. This isn't our end all either, because rifle shot for example has infinite high DPE but it's DPS is so low that it's not interresting to us either.
Of course we have to use a combination of the above abilities. In case of an ability like Corrosive Dart you'll want to look at its DPE and DPCT for longer fights. It will have very low DPS obviously, but if you look at the damage you do over its full duration (DPCT) it will be worth a lot more. Of course you'd normally also have to consider DPE, Corrisive Dart has the same energy as Snipe though (which is our energy based filler shot; so there really any use to compare in this case.
So lets look at the abilities we're dealing with:
Rifle Shot - 0 energy - instant (+1.5 sec GCD) - 0 sec CD :: This will be the lowest ranked ability in our priority. It does really low damage, but it's free and will be 1 of our 2 filler shots (assuming we're in cover). So whenever we drop below X energy, and we don't have adrenaline probe up, we will use this ability. X energy will depend a bit, and has to be theorycrafted. X could be 60 energy because that's where we drop to lower energy regen; however it could also be higher, because our other filler ability Snipe costs 20 energy. So whether it's worth using snipe with say 65 energy will have to be calculated as that means we'll drop to 45 energy. Is the energy loss worth the extra damage?
Snipe - 20 energy - 1.5 sec cast - 0 sec CD :: This is our other filler. It costs 20 energy but does more damage than Rifle Shot. It also procs Reactive Shots, Followthrough and keeps up Sniper Volley; so it's likely we'll be using this at least once every 6/18 seconds (I don't know if the buff duration of Sniper Volley stacks as well; might be more of an annoyance if it only lasted 6 seconds.
Ambush - 15 energy - 2.5 sec cast - 15 sec CD :: This is our big hitter on a long cast time. With such a long cast time it's likely not worth using unless Reactive Shots is up. It has great DPE though.
Series of Shots - 20 energy - 3 sec cast - 15 sec CD: A channeled ability that hits 3 or 4 times (I can't really tell, from videos it seems 3, but most databases claim its 4 so i'll keep this open for now) over 3 seconds. It's crits can also proc reative shots. And with the 31-point talent you can cast this 3 times in row. So with that in mind I'm assuming that Bioware want this to be one of our best abilities. Probably one of the highest DPE abilities at least.
Take Down - 15 energy - instant - 12 sec CD :: This is our "execute" ability. I'm not sure where to expect this on the damage charts though. Generally such an ability does a lot of damage; but I've also heard that it's damage is roughly equal to snipe. (Meaning it's only better due to having better DPE and it's usable on the move).
Followthrough - 6 energy (talented) - instant - 6 sec CD :: Procs from Ambush and Snipe. This is our best DPE ability without question. You'll want to use this everytime its up. So you'll have to find a nice rythm to use this in combination with snipe and/or ambush.
Corrosive Dart - 20 energy - instant - 0 sec CD - 15 sec duration :: Our main DoT; assuming its worth it we'll be keeping this up
Frag Grenade - 20 energy - instant - 6 sec CD :: Probably our best AoE. Use on CD in those situations.
Supressive Fire - 35 energy - instant - 0 sec CD :: Most likely our energy costing filler for AoE; it's damage is low but it hits 3 targets.
What our actual priority will be depends on what the damage of the abilities will be (databases are way off atm) as well as the situation.
On single target boss fights I expect something like:
Followthrough (try to keep on CD)
Series of shots (try to keep on CD)
Ambush (try to keep on CD)
Corrosive Dart (try to keep it up)
Snipe (if energy > X + once every 6 seconds for Followthrough + Sniper Volley)
Rifle shot (if energy < X)
On AoE fights of 3 or more mobs I imagine you'll want something more akin to:
Supressive Fire (if energy > Y)
Rifle Shot ( if energy < Y)
And that is not considering the cooldowns we have. But i'll just leave that aside.
EDIT: As for extra info there are some good articles on sithwarrior.com forum