I have a dedicated healer (1 shammy healer, 3 shammy dps; 1 dk tank) and I think it's needed for instances (earth shield is awesome) - My other 80 is a druid dual spec'ed healer/tank which I leveled entirely as resto (well from 60 as it was a RAF granted to 60 toon) and a druid as boxing healer should be awesome - so maybe make it your main healer?