To the previous 2 posters: this isn't really possible because the combat log doesn't tell you which spell caused damage absorption, and therefore who cast it (
according to Recount's current author). Besides, depending on luck/gear/skill, it's highly random. Example: you did your job, but your tank avoided most hits, resulting in your shields not absorbing a whole hell of a lot. Does that make you a bad healer ? No. But a meter wouldn't show much.
Shields are preventive "heals", traditional heals are reactive. Important difference. The best way is to educate your group leaders as to your abilities and teach them how to use a Healing Meter. It's not as simple as a Damage Meter.
Also, give this a read:
4 Reasons Healing Meters Suck : World of Matticus