Healing is not broken as long you have any idea of what kind of group you're inserted into, it's harder to gauge that in a PUG environment than a pre-formed group, that is certain, however you can have a slight idea of what kind of healer you have to be just by seeing how a group performs. Are tanks not using CD's appropriately to mitigate busters? DPS slacking on mechanics and require more of your attention? Then focus on healing only and maybe DPS when deemed safe so you don't end up risking a wipe or running OOM from too much healing. It's all about adaptability and healers have it worse in that regard since they need to have an idea of what's going to know how to act.
Fortunately in a pre-formed oriented group aka static, it's easier to adapt since you kinda know what to expect and not rely on the holy RNG of DF/PF where you won't know if you're either paired with a bunch of noobs or world class players.