Just my few cents... is there actually a way to know what story quest objectives will trigger cutscenes when you complete? If not would it be too much trouble to have the game check a player's DF status when a player goes to complete an objective and warn him/her prior to actually advancing with the cutscene?

I myself have never run into the lockout problem and rarely miss commencement times, and I main a DPS job. That being said... I also don't use DF as frequently as other people, so I can't say if my contribution means much. All I can say is plan ahead the best you can and watch the time and party status so you can get a sense of when to expect the commencement window.