I find treating everything as a single heal pretty much works ok. Specifically for shaman, I use the group heals as first choice over single heals. My personal order on macros is Unity of Spirits if below 30 > Fast group heal if target is sub 40% > normal group heal > single target > single target that hurts me. I don't actively use many of the targeted AE due to some targeting issues youll run into and the fact that I keep group HoT up perma so I rarely have deaths anyway, but if I was to work it in, it would be after the other 2 group heals just out of convenience of not interfering with UI.
Now if my shaman was out of group or I was playing any toons out of group, it would jump to number 1 on the list for obvious reasons.