A character ought to be more than the relationships defined by its class features.
My question to the boards: What are some paladin/cleric/oracle character arcs you've seen that go beyond "I'm a servant of [insert entity here]?"
Any paladin concept that does not begin at, "I AM a servant of [insert deity]." Which - for me - is basically every paladin I've ever played for 40 years (which is a lot); not a one of them was defined to any degree by their choice of deity. Their common core was that they wanted to promote good, and to destroy evil, and that's pretty much as far as the choice of class went. Everything beyond that was not defined by class features but by all the other stuff that
wasn't class features. I confess, however, that I had a leg up in first playing a paladin in 1E, which was not saddled by the rules with restrictive baggage of extensive oaths and fanatic devotion to deity-dictated concerns and endless attempts at re-defining and changing what the class was. That's the sort of thing that later editions quite successfully used to
narrow everyone's idea of what paladins
could be.
Maybe just put roleplaying ahead of mechanics. I mean, you say a character shouldn't be defined by just class features, but then are asking what there IS for a character beyond just class features? That's going back to roleplaying 101. First decide what your character will ideally be like, and
then choose a class that fits that concept most closely. When leveling up and making choices regarding your characters
mechanical improvements, choose on the basis of what does best at fulfilling that original concept. During play, when making choices for the characters actions that
aren't really connected to class mechanics, choose more on the basis of what the character was originally intended to be, or based upon the directions that the characters life circumstances has taken them, rather than a mechanical "build" that the character has to eventually adapt to fit.
Every character has two aspects of what makes them who they are. One is their mechanical stuff; their race and class abilities, skills and feats, and the stuff that magic items let them do. Stuff dictated mechanically by the game rules. The other is... everything else. In order to develop a character beyond just their class features, all you need to do is stop obsessing over just their class features and actually
look at everything else.