Adam is entirely dull. The First never really makes sense, which is a pity because it's a good idea.
I don't think we're supposed to feel sorry for Warren when he dies*, just be shocked at what Willow has done. I think Warren is supposed to be more dislikable than any other villain, despite or perhaps in part because of his banality - and I think the show succeeds in that.
*according to the comics, he doesn't actually die - Amy saves him and they get involved with a military organization trying to bring down the slayer army. Season 8 is pretty ridiculous, not really in a good way.