Ok, this is from 65 Cleric's perspective. Everyone seems to have an opinion that Clerics do one of two things, they heal and they melee. While I do both, melee mostly when I am solo/duoing or in a small group where more DPS is needed and tanks don't really need heals that much, those aren't the only things I do. Here are some of the things I do on most xp crunch sessions. First of all, I do buffs. This is simple, usually I do HoV on the group and BoR to all the casters. Sometimes when we are in a very dangerous area where any down member can mean a wipeout, I cast Devine Intervension on the MA and CC, usually the chanter.
When the mob is pulled, I also cast reverse damage shield line of spell on the mob. I also have mana free hammer pet that does decent damage so I cast that as well. I usually have root out just in case we have some issues with unexpected adds, specially in an area where CC can not keep up with all the adds. Also, I always have my stun out. When a mob is hitting on the poor Chanter who keep getting mez interrupted, I throw in a quick stun to give the Chanter chance for the mez. Both root and stun works well when there is no snarer in the group. I usually stun, my stun lasts 8 secs, and that takes care of the mob. If not, just root until finished.
Finally, healing to me is an art. You have to understand the players' statistics as well as mob's abilities to keep the healing time down. The real artistic talent is shown when the you-know-what hits the fan. I always make sure not only the tank survive, Chanters survive too. When there are 3-4 PoP level mobs are hitting on the tank and the Chanter, there is where the fun begins.
Doing all of these things certainly keeps me busy while in a group. To me, Cleric role is what you make out of it. You still need to sit/mount med between the beginning and the end of the battle to get mana back but if mana is not a problem, just go all out and keep busy.
Taushar