The character was never meant to be the leading man. He was a supporting character in Buffy's story and I'd say his role overall was actually tertiary rather than secondary - the main supporting characters were Willow, Xander and Giles. Angel comes after that in the ranks, and only comes to the fore when it's necessary to Buffy's story.
Buffy was a female leading character in an American 90's teen show, it would be unthinkable for her not to have a leading man. He was such a leading man he went on to get his own show. I'm not sure a secondary or tertiary character wouldn't have had such a risk taken on them.
There are scenes of obvious melodrama like the early S2 stuff (Some Assembly Required), but it's Buffy driving it and it fits at that point because she is a teenager after all so she's allowed to behave that way at least a little. But then there are more quiet down-to-earth moments like 'Earshot' which provide a nice counterpoint to the high drama. I actually like the moment in 'Graduation Day' when he does raise his voice a little during their argument. It brings in a bit more emotional variation and frankly it would be even more unrealistic to expect him to remain steady calm all the time. Just because he is by default reserved doesn't mean he can never get worked up.
Yes this is where my disconnect with Angel begins. Buffy is a teen girl, she's meant to be dramatic, but Angel is a brooding 240 year old, what's his excuse? He encourages Buffy's exaggerations, when he should be a calming, quieting influence, he's actually the opposite and all too often encourages Buffy's drama. That, for me, doesn't work with the personality we have been told Angel has.
I think it would be difficult to do their story without an degree of melodrama because it is written to be 'big, world-in-peril stuff'. The situations are extreme (gypsy curse, world getting sucked into hell - the circumstances are very life-or-death) and the characters have to respond to that in a heightened way for the story to hit a dramatic high note, even if they do mock/snark about it afterwards. That balance is part of the joy of the show. Melodrama actually drives the whole series- without it it just wouldn't work because it uses melodrama via larger-than-life fantasy and horror tropes to access a deeper psychological and emotional realism for its characters.
I would agree with this. In the early seasons the characters are metaphors, they don't need to be nuanced and so the melodrama isn't too jarring. But it is there and many fans deny that bangel was melodramatic, which I would totally disagree with.
