Healing classes are in alphabetical order
Druid
Paladin
Priest
Shaman
Druid healing = hots
Paladin = I've never seen someone that can spam FoL better than a paladin
Priest = a lot of escape healing
Shaman = Chain heal Spam FTW
In raids it is nice to have a least one Druid and one Direct healing class. 25 mans you have about 7 healers. This leaves lots of options. But we will stick to 10 man for now.
Druid/Direct healer combo
3 stack of LB ticks for about 600 on a druid with 1400+ healing and Rejuv ticks for around 950 every 3 seconds
This takes the strain off of direct healing classes. If tank takes a Big hit, the hots are right there to pull him back up, even if the Direct healer had just tapped escape and has another 3 seconds before next heal can get off.
Pally/ Priest combo
Pally Spamming FoL as fast as possible, Priest escape healing and Renewing on people
Druid/ Shammy
Difficult combo if not really well geared, the hots are there to bring tanks back up from big hits, but Shammies can pretty much ONLY spam chain heal, anything else is ineffecient.
All the times i've been in Kara we 3 heal it. Even with 2 uber healers, a 3rd is nice to have if you have enough DPS. Our combos so far have been:
Druid druid priest; Druid priest priest; Druid shammy pally
About getting healers-
Spam trade channel. saying you are recruiting healers of any class and ability. do weekly instance runs to get them geared. Get a steady tank. Be willing to at least try Attumen or even the trash pulls up to him, there are a few epics that "Could" drop just off of trash. Don't be afraid to wipe in raids, it happens even to the "Leet" groups.