When a card splits, I think it's best to add the health and average the attack in terms of evaluation. So belcher would be more:
5 + 2 + 3 * (5 / 7) + 1 * (2 / 7) = around 9.4 stats, plus taunt for 10.4 stats which is par for 5 mana.
By the same measurement, harvest golem is 6 stats for 3 (par) and haunted creeper is 5 stats for 2 (par)
5 + 2 + 3 * (5 / 7) + 1 * (2 / 7) = around 9.4 stats, plus taunt for 10.4 stats which is par for 5 mana.
By the same measurement, harvest golem is 6 stats for 3 (par) and haunted creeper is 5 stats for 2 (par)