They definitely didn't really think this through. You're absolutely right in that a lot of the healer/tank role actions are essential, but the way it's structured now you are granted the illusion of choice.
As someone else mentioned, you can give the tank/healer roles additional role action slots, so that you're not restricted due to 4/5 spots being necessities to begin with.
Not sure giving each job uniquely named, but similar skills, would be the right course of action. Seems like a step backwards in what SE is trying to accomplish.

Either way, something needs to be adjusted imo.