They're all worth four mana. Huffer has the stats of Arcane Golem without the drawback. Misha has +1/+1 over Ironfur Grizzly and the same stat total as Tazdingo. Leokk... has the stats of a three-mana minion and an aura of unknown value (no directly comparable cards), which is probably fairly valued as worth one mana. Unless you meant they're literally three-mana cards, in which case carry on. ;[ That's true, they have a 3 in the blue gem.

Animal Companion is allowed to be this good both because of the random element and because it's a class card. It's undoubtedly a great three-drop but it's not *too* good.