To add back to this thread with some explanations.

I have an 80 lock that I raid with, I also multibox with him.

While boxing or running guild instances on trash I just hit every mob in the pull with corruption, that's it. It does enough damage by itself without risking agro and allows you, with both the talent and glyph, an 8% chance of proccing nightfall each tick. With the nighfall procs and weaving SB when it doesn't, there is no need to use anything but those two spells on every trash pull.

On bosses my rotation is CoA, Corruption, SL, UA, Haunt, SB spam until dots start falling off and then reapply and repeat. Drain Life is NOT as good dps as SB spam and should not be used on bosses or trash unless you need to get hp back after tapping and healers are busy, and even then you should have imp out and be dark pacting from it for mana before tapping.

You will never get 100% uptime on dots, and SL will be the usual casualty just because of it's length and the fact it's easier to just refresh it when you refresh the others but it has the benefit over something like CoA that it's damage is consistent across it's duration so you don't really lose dps when you reapply it, it's just not as mana efficient as it could be.

The final thing I'll add is that I don't use a cast sequence for my dots, I prefer the granularity of having each one a seperate button due to resists and misses. With the increase in hit rating needed as you level (going from needing 202 hit at 70 to 372 minimum at 80 if you take suppression and bane) you will find yourself missing with dots more regularly and will need to have to try to reapply them, but with them in a cast sequence you won't be able to and you will be gimping yourself more in dps. For example, at 80 now in reasonable mix of pre and post LK gear I'm still only at 286 hit and on a recent Occulus run I saw haunt and UA miss a fair few times on bosses (perhaps the others as well but I don't really pay attention to misses on instants) and if I had a castsequence macro for them I'd have been missing out on some good dps along with heals and other benefits to those spells.

Bottom line for me in helping here is:
* Get DotTimes add-on
* Don't use cast sequence
* Go for +hit gear as you upgrade unless you are hitcapped at your current level each time
* Get glyph of corruption
* Use only corruption and SB on all trash mobs, making sure to dot every mob each pull before starting to SB skull
* Never use drain life over SB on bosses unless you need to heal after tapping

Give a few instance runs a try using those suggestions and compare it to your dps using your current set up and I almost guarantee you'll see a signifcant increase to your damage output.