"Minimal"? How is going from toying with someone to being so furious with him that you will stop at nothing to kill him minimal development?
That's not character development. That's just a harder boss battle. Trying to fight your hardest in someone who might actually kill you is no development. It's common sense. And like Cfrock said, Ghirahim never slowly begins to acknowledge Link's power. He just gets annoyed and decides to kill/stall him.
It... does. Each encounter, Ghirahim gets more and more frustrated with Link. I don't see how you could say otherwise. It happens directly in the game.
Getting ticked off at someone for going out of their way to stop you from achieving your goals isn't development. It's common sense. And actually, no, he doesn't get more frustrated until the end.
Skyview Temple: He teases Link and says he's in a bad mood and needs to torture him.
Earth Temple: See above. Except this time he uses a monster to do it.
Ancient Cistern: He's bored and more or less does it for the lulz.
Fire Sanctuary: See Skyview Temple. He decides he will kill Link for not revealing where to find Zelda. He's not openly frustrated and merely teases him.
Final Battle: He's finally ticked off.