I ran around for a couple weeks with "passive" healing setup on my dps sham using this construct:

Code:
/castrandom  lb,cl,,
 /cast [target=targettarget] lesser healing wave
I ended up ditching it because it was throttling my dps more then I wanted and overhealing by a fair margin, but it did keep the heals rolling and I very rarely had to hit my dedicated heal key.