My current setup, I have tried to keep most of the timers and information down in the center as most in-game action happens there.
Having most of it centered makes it easier for me to keep track on cooldowns and at the same time keep an eye on whats going on in the game world.
I can see that some got their player frame and target frame split on the far left and far right, i don't think that is optimal at all for gathering information quickly.
Having targettarget as i have it feels for me to be the best way, as DPS I quickly notice any target change and can quickly pop Icebound Fortitude or Anti-Magic Shell if the mob is targeting me, if I'm tanking i can quickly notice if I loose aggro.
Some of you may notice that it looks like I have both blood aura and unholy, it's not, but a a fake "buff" I made with oUF to show what presence I'm in.
Important addons that are in use
MagicRunes: rune tracking
ClassTimer: for tracking player buffs and target debuffs, buffs placed below player frame (Blood Fury, DRW+) and my debuffs on the target below targettarget.
TellMeWhen: (not visible) pops up as an icon above the rune's to show when ever Death and Decay and Horn of Winter is on cooldown.
DocsSwingerclub: nifty swing timer makes it easier to track when your slow two-hander is going to hit