Well, pre-u14, healing is not fun. Being new to endgame content is not fun. I TR'ed my healer into dps for that reason. My friends have left DDO for those reasons.
People built to have 1 tank in party who cared about miss chance, partied with a lot of experienced players who built to large HP or self healing or tons of healing amp. New players that didn't know to build this way and/or didn't have the gear for it were stuck in a "reroll or don't raid" situation.
Healers had to cast a LOT meaning a lot of SP usage, meaning more babysitting than any other game I've ever played and more expense to the healer than I could have ever imagined when I first rolled mine up (in the form of major SP pots needed for raids). Combine with almost no healing raid or endgame gear compared to all the DPS, tank, and casting gear, and being a healer in DDO was not very much like healing in an MMO at all.
What needed to happen to fix these issues turning away healers and new players of any role: Make miss chance more of a mechanic, make super-HP less of a mechanic, GET PEOPLE TO BUILD AND PLAY DIFFERENTLY SOMEHOW.
Now here's what it seems/I hope is happening post-u14 to get us there:
U14: Make miss chance drastically more of a game mechanic & make small amounts of heal amp more available in the form of randomly-generated gear and the PDK gauntlets. Expect players to start building to miss chance (including free LRs) Make super-ramping heal spells less viable as a way of getting them to move to the new paradigm.
?: Make super-ramping HP less possible to non-barbarians. Perhaps by limiting Toughness to a single-use feat.
And if vets continue to not change their ways, they'll have to find more and more creative and nerful ways to try to get vets to move to the new playstyle that WILL be more fun for more people.
Now MY concern is that we help out the HEALERS durign this transition by providing them more BTC sp potions via all their epic end reward lists or somesuch.