Brock's Happiny is there for comedy relief.
And just happens to be pure epicness aswell.
Yeah, most Happiny are pathetic. Just like most Chansey and Blissey (minus that one that was friends with Jessie. TR Bliss ftw!).
Not saying that family's pathetic. They're, in fact, some of the strongest competitive pokemon around! Chansey is probably the only nfe pokemon in UU. Although I think Scyther might be aswell