[Phanx]

Many things, all sides!

(1) Get rid of that combat text. You already have icons for Windsong and Divine Insight on your player frame. Expand that to show all the proc buffs you NEED to know -- if you're not going to do something special when it procs, you don't need to see it. Filter the debuff icons on your target frame, too. You're a shadow priest. You don't need to see Thunder Clap!

(2) So many action buttons! Survey, Fortitude, Resurrection... none of those are ever going to be used in combat, so put them on a bar that only shows up out of combat, or stick them in an OPie ring. Keybind long cooldowns and get them off your action bars. If you have trouble keeping track of the cooldowns, try CoolLine or SexyCooldown, or some other cooldown monitor. Showing action bars on hover promotes clicking, and clicking is bad, mmkay.

(3) This is mostly personal preference, but your unit frames look really cluttered. The texture doesn't help, but you can't even read the dark blue mana text on your player frame. If you can't even read it, just get rid of it!

(4) More personal preference, but if you're trying to reduce clutter, set that Broker bar to hide until you mouse over it. You do not need an always-on display of how many friends are online, how much gold you have, what your framerate is, or how many open bag slots you have.

(5) For the sake of balance, move that damage/threat/whatever meter over to the bottom right underneath the tooltip, so it somewhat balances out the chat box on the left.

(6) Unless you're a tank on a multi-tank encounter, you don't need a threat meter. Add an indicator to your target frame showing you the basic yellow = high threat, orange = you're about to aggro, and red = you have aggro, or showing your threat as a percentage of the current tank's threat.

(7) I don't see a combat log in your screenshot, so I don't know where you intended for more meters to show up in combat.