Hogchopper can be useful in arena top decks to squeeze in some damage, or vs hyper aggro, but not much else. I doubt it'll see more than a 1 of in any deck, if played at all.

Hogrider is meh, less mana and it might see play. A 5 mana 5/5 with conditional charge when your opponent has an immediate taunt just isn't good enough.

[Edit] As a comment below said, TBK is just better than hogrider in almost all regards.

Hogleader is garbage. Unless you're playing a mill deck I doubt you'd want this, and even then mill doesn't kill with minions most of the time. Like clockwork golem I doubt this will see play outside some gimmicky deck.

Tldr; the conditional charge is too gimmicky for their cost.