what i did was make macro's on each char,
on F1 on every char is /cast [target='charname1'] Lesser healing wave (rank1)
on F2 on every char is /cast [target='charname2'] Lesser healing wave (rank1)
etc etc

and i use a LOWER rank than max for this, just counting that 4x (or in my case 5x) lesser healing wave 1 equals 5x 200 health, 1000 health, in 1.5second cast time
when one char is in need of healing, i mash the corresponding F-key, and he gets healed by all back to full
on my F6 key i have bound /cast [target=player] Healing wave, withouth a rank added, this casts the biggest heal on each char, i use this after a big AoE fight or fall damage.
Now that i hit lvl 40 i can add in chain heal to the mix for that

than on my 2 button i use
/cast [target=focustarget, help, nodead] Lesser healing wave (rank 1); [target=focustarget, harm, nodead] lightning bolt
this way i can target someone (npc, some other player, etc) and cast a heal
my number 3 button is the same, but with chain heal and chain lightning

and yes i use focus for this setup, you can change it to use /assist 'name' or other way you use