In my mind, cure/medica is your standard way of dealing with damage, regen/medica II is how you heal people who took just took a fair bit of damage but won’t be taking any more damage soon, and cure II/III is how you heal people who are taking major damage or need to be healed a lot in a short amount of time. As other people mentioned, proper use of cds and knowledge of the fight will help minimize the amount of “oh shit” moments you find yourself in.