Were Defiant-class ships difficult to operate because too much equipment was packed into too small a hull?
Short answerYes, but the problems also reflect Starfleet relearning how to build a compact pure warship, and could be reduced as the class matured.
NotesThe Defiant design is unusually demanding, but that may reflect institutional inexperience rather than an unsound concept. Starfleet had not attempted such a concentrated warship for a long time. Continued construction and operational use could work through the faults, as happens with many otherwise successful ship classes.