Right now, only shaman actually has a normal AoE heal. This makes it necessary to have a shaman for the normal passage of the content.
Why don't we try to balance the other classes a bit? I have a concrete proposal, but it needs testing.
Current situation :
Shaman Chain heal - Heals the friendly target for 170 to 208, then jumps to heal additional nearby targets. If cast on a party member, the heal will only jump to other party members. Each jump reduces the effectiveness of the heal by 40%. Heals 3 total targets.
CD - No cd ( only gcd ), skill can be spam
How is scales - +134.28% of spell power to direct component
Priest CoH - Heals up to 5 friendly party or raid members within 15 yards of the target for 133 to 169
CD - 6 sec cd
How is scales - +40.20% of spell power to direct component
Dudu WG - Heals up to 5 friendly party or raid members within 15 yards of the target for 119 over 7 sec. The amount healed is applied quickly at first, and slows down as the Wild Growth reaches its full duration.
CD - 6 sec cd
How is scales - +11.50% of spell power per tick
My suggestion is to up CoH and WG scaling. That's will make raid setup a lot more flexible.
CoH to + 85% of sp to direct component, WG to + 75% of sp per tick