Okay, a few changes I would make. Either get rid of or change the scale of sexymap. Yes the swirly blue thing looks cool but it also takes up a significant portion of your screen for absolutely no reason. I would switch to simpleminimap or squeenix (personally).
As for addons that can help your DPS you can pick up Scorchio2 (or it may have just gone back to being Scorchio) -- it will help keep track of debuffs and procs, etc and does a pretty damn good job of it.
You could also pick up cooldowntimers2 (I think is the name) it will remind you with a flash on the middle of your screen when your cooldowns are up so you can use them again soon (if you need to).
I see 0 reason for you to have healbot installed, you aren't healing, at most you just decurse. There are a couple of common options for this: 1) get decursive, it is lightweight and just lights up the bubbles that are cursed with pink or blue if they are MCed and can be sheeped (friendly targets of course). Or install Grid (raid unit frames) and use an addon like Clique to give it functionality that I listed for Decursive.
For castbars the standard is pretty much Quartz. It takes about 5minutes to get used to how to change the settings with the interface, but when you get it you can move/re-size anything you want pretty easily. Just /quartz go to the one you want to change, uncheck 'lock' and move it where you want to and resize it etc.
IIRC slidebar is the thing that sits to the right side of your monitor that when you hover over it it will pop out. I think Auctioneer uses that.
I use PowerAuras to remind me of procs (hotstreak/missile barrage) as well as Scorchio to make sure I don't miss them. Using MSBT (mik's scrolling battle text) also helps while it is scrolling and you can set a sound to replace when the proc happens.