To be fair, English isn't his first language. It's quite hard to be charming and funny in a different language and he obviously hasn't grasped it yet. For all we know, he could be outgoing and have more of a personality with his own friends or colleagues. But I do agree that Mary is choosing him for the wrong reasons and he's not a long-term prospect.
I liked Christine for a while and then realized that she is sometimes the very thing she calls other women—two-faced. She spends some alone time with the women to get more info out of them (probably egged on by the producers), shares stories with the women and seems like she relates, but then goes on the attack when one aspect isn't to her liking or something rubs her the wrong way.
Davina is the worst. She's just a bummer and full of jealousy.