I don't really pvp, so I can only share what I do in a pve setting. Also, this is just a rotation that I use, I have friends that do things a little differently and parse just as well (and sometimes better ).
Here's a parse, if you want to see what I actually do: http://parsely.io/parser/view/337942/0
The thing I focus on is pinning my DoTs to my lethal strikes for convenience. You'll see people do this differently, but I try to keep it simple and just do something like:
Lethal Strike -> DoTs -> <Insert Filler Here> -> Lethal Strike -> <Insert Filler Here> -> Lethal Strike -> Dots -> Repeat
After that, it's simply a dance of getting as many tactical advantages (TA) you can to Corrosive Assault for days. A few things to keep in mind:
1) Stealth out for your Lethal strikes to get a TA. Grab the utility to get TA from holo traverse, and stim boost gives a TA as well. Remember that Stim Boost gives 10 energy (and an alacrity boost), so it can be well timed to save you from dropping below 60 energy.
2) Shiv isn't all that great, but you really want the proc it gives every 9s for the extra TA and free Corrosive Assault. Of course use it if there isn't anything better, but it's not something you always want to use off cooldown.
3) The way my rotation works, there will be gaps where you can't generate or spend tactical advantages. The way I see it there are 3 solid filler choices: Overload shot, Sever Tendon, and Rifle shot. Use rifle shot if you're watching your energy. A lot of people use overload shot as the other filler, but for some reason I have a soft spot for using sever tendon + the utility that grants TA. I'm still experimenting with this a bit actually.
4) For AoE, Lethality is simply terrible for weak mobs. For stronger mobs, I tend to throw a dart as the adds start to group up, Toxic Haze to spread dart as they start to clump, corrosive grenade when they're nicely mobbed, then Noxious Knives until only 2-3 are left standing. It won't beat a sniper, but it's actually pretty effective.
5) In a real fight, you still suffer from a lot of weaknesses that most melee dot specs have: range and target swapping. However, Lethality is still extremely effective at 10m range. Use this to your advantage to keep up strong dps on moving targets or to avoid circles. Also, your dots (and rifle shot) are 30m, so you can apply those as you are moving between targets and keep up your rotation more or less. Between the off heals (kolto probes) and the 30m dots, there is rarely an instance where you character is doing nothing in a fight.
6) Practice abusing the reflect damage on evasion. Won't make or break your dps, but it helps you keep up with your raid team's jugg if you're lucky
Anyways, that's just how I play my operative for PvE, definitely not the only way. Hope it helps a little.