I use a number of things to streamline my UI when it comes to healing.
I feel it looks very clean and elegant, for healing I use Grid and Clique. I was originally a healbot user, but after I sat down and said "Before I do ANY instances today, I'm going to setup grid" I fell in love with it. I have it set to where it will expand to 25 frames in a 5x5 pattern very similar to the 5x2 it's set at now. I've actually moved my health and mana numbers since this screen was capped but I'm at work and don't actually have access to my new screens yet.
Mods I use to Achieve this Interface Bartender 4 - I use this for all my bar setups. In different forms/classes I'll have an additional bar from the ones displayed floating out in my non-blackened display with important spells (i.e. Blink, Ice Block, Evocation, Frost Nova on my mage.) For the bottom bars I have them at a 0.75 scale to fit into the black bars.
CBH Viewport - This is the addon that causes those black bars on the top and bottom of my screen. Yes the addon is "out of date" but it doesn't need to be upgraded patch to patch. I have it set at 140px top and bottom bars with a 1280x800 resolution. These letterboxes ACTUALLY cause my view to get wider and is advantageous as I can see in PvE and PvP when an enemy is coming or when someone's under attack without panning my camera around the BG/Raid.
Grid - I use Grid to monitor HoT Status (Lower Left and Right dots on the names,) aggro, Poison/Curses, and health bars. Since I'm only posting what I use to alter the LOOK, I will go ahead and tell you that I use
Clique to have click-to-cast spells linked to my mouse when hovered over Grid.
MikScrollingBattleText - Simply put it has a much more streamlined feel than the blizzard UI's text.
Omen - On my Healer this is mainly a space filler to make my letterboxes feel a little less empty, though I do monitor threat on bosses to make sure I'm not going to have to Nature's Swiftness/Healing Touch some unsuspecting Mage.
Pitbull - My frames mod. I never display party or raid outside of Grid, but I do put my target and target's target up on the top part of my screen just below the letterbox and just above my Decursive. .
Prat - This is my chat box mod that puts the input box above my chat box, allows me to set it further into the letterboxes.
Quartz - A castbar mod that I have placed above my target (for me) and my target's target (for my target) though I didn't get any screens of it in use.
Recount - Everyone should have an idea what this is. By the way, I have it set to healing done because I scroll between that, action log, and overhealing done (I'm used to be healing lead/2nd heals and HAVING to watch this, it's just habit) to assess both my own and other individuals healing on a personal basis.
SatrinaBuffFrame - If you look in both screen shots in the top letterboxing, you can see where I display my Buffs (right side near minimap) and debuffs (In the second snap, left side opposite of buffs)
Satrina's Digits - Smack in the top middle I have my health and Mana numbers displayed. I find it much easier to parse the data from numbers than from bars. Since taking these shots I've changed these numbers to displaying percentages and being stacked on top of one another closer to the debuffs side of the screen.
Squeenix - Yeah my mini map is square.
Ha, you had to go look didn't you? I've never been fond of the mini map, I like corners and such, much more pleasing to my eyes, this is a PURELY COSMETIC decision, and it allows me to move the mini-map to anywhere I'd like.