Honestly? I don't use a healing add-on. I use the wow raid frames + mouseover macros. Every single one of my healing spells is key-bound.
Click healing is incredibly slow. Just using mouseover macros will increase your reaction speed by an incredible amount.
This. And WHICH mouse over you use makes a huge difference.
/cast [target=mouseover,exists] Flash Heal
With that you can have whatever you like selected, it's just where your mouse pointer is that matters. Then you tap your keybind.
/cast [nomodifier:alt,target=mouseover,nodead,help][nomodifier:alt,help,nodead][nomodifier:alt,target=targettarget,nodead,help][nomodifier:alt,target=player][modifier:alt,target=player]Greater Heal
This one looks complex, but isn't (and there may be a simpler format, I've been using this one since BC(?) days.) I can vouch it works, just replace "Greater Heal" with whatever spell you like But here is how it reads:
The macro casts on a single target, in the following order:
1) If target is friendly
2) If the mouse is over a friendly target
3) If the target is hostile, then on the target's target
4) If no target, then player
5) If alt held, player no matter what is selected or who mouse is over.
As disc this works especially well, as I can have the enemy selected the entire time and heal off it.
Wowwiki has an amazing collection of macros, which is where I originally got this one from.
Some of them ARE outdated, so read before you copy.