I raid hardcore as a Resto Druid, so this is what I would do...
Grid
This is your most important add-on, as it serves as raid frames, hot timers, dispel alerts, agro alerts, etc. You need four add-ons, they are
Now, to configure it will take some time. First, in-game type /grid config
Click + to expand the Frame options. This will help you choose what you see and where you see it. Go through each section (Border, Healing Bar, Center Text, etc) and check the boxes as follows...
- Top Right Corner (Aggro alert, Buff: My Wild Growth, Incoming Heal)
- Corner Text Top Left (Buff: My Rejuvenation)
- Corner Text Bottom Left (Buff: My Regrowth)
- Corner Text Bottom Right (Buff: My Lifebloom)
This will allow you to see all your buffs on targets as counters, thusly

note I don't have any Lifeblooms up, but if I did, they'd be bottom-right. Also note I monitor who has PW:S so I know the urgency of my heal. Finally, note our tank, rather than his name, it displays +34.6k. This shows that he has a heal incoming (from another healer).
Play around with grid - it is an extremely powerful addon.
Macros
While you're in-game we need to set you up with some mouseover macros. If you've never heard of these, allow me to explain. A mouseover macro will allow you to target someone for a heal, simply by moving your mouse cursor over them, rather than physically clicking on them. The advantage is two-fold.
- You get to maintain your current target (I usually target the boss so I can monitor health)
- You save about 0.1 secs. While that's not a lot, over a 5-minute boss fight, that adds up to 20-30 global cooldowns. Think about it - you could get in 30 more Rejuv's than the guy right next to you that still targets manually.
So here we go, take the following steps:
- type /macro
- Click new to create one and name it Rejuv (leave the icon blank)
- type:

(it formats funky when I try to type it out, but make it look exactly like that)
- Now do that for all of your spells (Rejuv, Regrowth, WG, LB, SM, Innervate, Brez, etc)
- When you get to Nature's Swiftness + Healing Touch, type this:

- That macro will allow you to mouseover someone, click your button twice, and cast an instant Healing Touch
Cooldowns
Our next addon to discuss is simply called Cooldowns - download it here and download it now! This is what it does:

See the 2.3m over my Nature's Swiftness button? That indicates to me that my NS is on a cooldown and will be available again in that time.
But, if your bars are at the very bottom of your screen, that just won't do (as your eyes need to be constantly monitoring Grid. Create a new bar in Bartender and move it near your Grid and drag just those abilities with cooldowns you need to monitor.
Other Very Useful Addons
I won't go into great detail about configuration, but the following addons are all near essentials for a great raid healer...
X-Perl is more user friendly and easier to use, but Pitbull is more customizable
Allows you to customize the crap out of your hotbars
Is a damage meter that gives you tons of information and stats on your healing
An extremely customizable and powerful addon that lets you monitor buffs and cooldowns (alerts you when you have Innervate, Heroism/Bloodlust, etc)
Overall Interface
In the end, put a lot of thought into your configuration and do what works best for you. This is what I do (here's my overall UI)

You will notice I have all the important information centralized in the middle of my screen. This means, without moving my eyes, I can:
- monitor Grid
- monitor my Cooldowns
- click on non-keybound items (potions, Barkskin, etc)
- view my HP and MP
- keep an eye on my target / ToT / ToToT
- keep the play-field and boss in my peripheral vision
- glance up if I need to focus on the play-field or DBM warnings
This is a blow-up of what I stare at 90% of the night...

Notice, aside from DBM warnings and play-field, I have everything consolidated closely.
Also, AND VERY IMPORTANT, my mouse cursor never leaves this area - EVER. It may save only 0.1 secs to move your cursor across the screen, but that's 0.1 secs that you cannot spare in a Heroic Putricide, for example.
Conclusion
We all must do what suites us best and everything I've said above is opinion and open to debate. But I have been healing for 5+ years and this UI has taken me that long to develop. My philosophy when developing a UI is to keep these things in mind:
- Maximize the amount of useful information you can give yourself
- Minimize the junk (combat text, etc (note I've since disabled it)); don't distract yourself with crap that doesn't help you 1. to heal better, 2. to survive
- Consolidate everything you need into one compact location
- Minimize the area of your screen where your cursor resides - don't have your Grid frames and your clickable abilities too far from each other
Hopefully this has been helpful.
Epicmedic - < Sometimes There Is Fire > - Icecrown (US PvE)