I havent tried the latest verions yet, been off a couple of days. But from my experience and logs i've read this is how priorization should be. And note, its not an "easy" on thare are a couple of "IF's".
1. Cast Marked shot - but only IF you dont have the focus/time to hit Aimed shot before vuln buff dissapear and MUST hit Marked shot before buff dissapear.
2. Cast Windburst on Cooldown.
3. Cast Barrage on Cooldown.
4. Cast Aimed shot - but only IF you make it to HIT target before debuff dissapear, so casting at 2sec with a casttime of 1.7 is not optimal if you are at far range. To be "sure" it's better to cast last aimed shot at 2,5 sec left off debuff.
5. Cast Sidewinders if Marketing shot buff is UP, otherwise wait 2x stack and cast it (If Windburst/Barrage is up that is prio ofc).
Sorry if much info and I understand if bot cant understand all this, but this is simply best rotation. If you can do above its great, if not the closest to it would be best.
Everything with MM is about Vulnerable stack - if you cast a single aimed shot without it, it's a huge dps loss.'