To my knowledge there is no way to make party order consistent between multiple characters, aside from the party/raid leader

The way I do healing (I use 1x DK tank, 3x DK dps, 1x resto druid...I only use DKs as my leaders and never the druid) is to dedicate 5 keys for healing use only with statically defined targets. So each macro includes the targeting for the respective toon name with modifiers to control different abilities. Too keep all this intuitive and consistent I order my raid frames alphabetically (I use pitbull) so that the key order matches up with the display order of the health bars for all characters

sample healing macro:

/castsequence [nomod, target=toona] reset=7 Rejuvenation, Lifebloom, Lifebloom, Lifebloom, Regrowth
/cast [mod:alt, target=toona] Swiftmend
/cast [mod:shift, target=toona] Nature's Swiftness
/use [mod:shift] 13
/cast [mod:shift, target=toona] Healing Touch
/cast [mod:ctrl, target=toona,nodead,help] Regrowth
/cast [mod:ctrl, target=toona,dead,help] Rebirth

hth