A few things could revive Healers as a whole. Like reverting resurrection back to the way it was in the first place, letting Healers also raise Evils by making them Neutral only, and add in DI for the Neutral only religions that don't have them because it wasn't needed before. Revert many of the drawbacks imposed upon them and make them strictly no PK and limited to rares/unique items, and then make 1 resurrection give the full +50 hitgain and such until they die. Or keep them as is and make it so they can still kill, but with the guidelines they already have. If they limit rares, make them able to use 10 rare items or 5 unique items or a combination of either where 1 unique basically equals 2 rares?
I honestly enjoyed them back in the day and thought people never utilized their full potential for the most part, but I believe only 1 player other than myself really ever capitalized on the whole "walking fortress" aspect Viri said they were if played right. They still have a lot of potential, but honestly a Druid is far more fun to play than a Healer and even a Berserker is more fun than a Healer in terms of survival. I can't solo the Offices as a Druid or a Healer though without other factors at least, but it's pretty easy as a Berserker if you're wanting to do thing alone and live.