I just dual specced one of my pally slaves as a healer and have her stand back and spam Flash Heal in a macro. It's on the same button as my DPS and Tank's main spam. The macro I'm using and seems to work very well so far, is:

#showtooltip
/assist focus
/cast [help][@focustargettarget] Flash of Light

I've got another one like this for Holy Light and Holy Spark as well.

She don't cast it if she doesn't have anyone selected, and will constantly heal whatever her focus's target is. Be it me, or someone else in the party that draws aggro. Down side I've noticed so far, is I have to setup a separate heal macro to heal herself if she somehow gets hurt from AoE damage or by an add in a mob I'm not targeting. I now have my numberpad on the right of my keyboard setup to target party members through the Keybindings interface and a macro on Num-5 to cast FoL as well. I'll get into using ISBoxer later, but for now, I'm still using Keyclone only. I saw the vids of how to set up for healing and liked it. I've got a priest on my 4th I'd like to use as a primary healer once I get her to 80. Right now, my main Priest healer is 68 and leads 3 Hunters using Healbot to heal.