I was dualbox healing Priest/Druid and it worked very well, with a sympathetic group about cleansing. Cleansing the tank and cross cleaning between the characters was all I really wanted to do, but are easy enough. At the time priest and tol druid were a great synergy for healing.

Technical wise, I click healed HKN repeaters and no repeater mouse over keypressed over the same raid unitframe, with some mundane heal MT1,2 keybind macros. Some stuff I had mapped to a xkey pro.

A lot of fights were stupid easy to heal through with the coordination, and basically gave the raid an extra DPS slot.

Things like cyclone, shackle, combat rez odd characters, mass dispell if I was unprepared, innervating others, that stuff sucked and frankly messing with it would cause more problems than it would solve.

Having someone(s) that your character can follow in advance is nice working out the separation anxiety issues is pretty key. If you follow some friends in AV and play in different areas of the map a few times you get a hang of it.