Well I don't know of an add on that will manage all your heals and decurses but I'm running a Pal tank(main) and 4 Priests and this is how i manage my healing/dispelling. I heal 2 diffrent ways but the keys are the same. One will heal your focus's target and one will heal will heal what ever member you push the key for. For decursing i use Decursive and have made the blocks bigger on my followers so if i need to i can look over and click them easily. It dosen't matter much that they are big beacuse i don't have to look at their screens for much anyway. Having decursive on your main Just know the colors and click on what class's screen that can dispell it.

These may be a little off since I'm at work but it will give a genral adea you can work with.

For the Assist heal macro: (Target with main and wait 1 sec before clicking)

#showtooltip
/assist focus
/cast [modifier:Alt] Greater Heal
/cast [modifier:Ctrl] Power Word: Shield
/cast [modifier:Shift] Renew
/cast Flash Heal


You can also make a macro for each toon this is faster cause ytou don't have to wait for the server to get your main's target before you cast)
#showtooltip
/cast [target=toon1,modifier:Alt] Greater Heal
/cast [target=toon1,modifier:Ctrl] Power Word: Shield
/cast [target=toon1,modifier:Shift] Renew
/cast [target=toon1] Flash Heal

#showtooltip
/cast [target=toon2,modifier:Alt] Greater Heal
/cast [target=toon2,modifier:Ctrl] Power Word: Shield
/cast [target=toon2,modifier:Shift] Renew
/cast [target=toon2] Flash Heal

I have these set to my F1, F2, F3, F5, F6, (skip Alt+F4 lol) one for each toon.