I think the Beast is possibly underrated, especially in control decks.
In control mirrors, it's a big threat that will either cause serious damage or attract premium removal which then won't be hitting your other big guys. Consider also that three popular ways of dealing with big minions (Tinkmaster, Hex, Poly) won't trigger his deathrattle. If they are able to remove him, a 3/3 is rather inconsequential in a control mirror. You'll usually have spare small dude removal anyway. Worst common case would be he trades with two mid-range dudes, or one mid-range dude plus mid-range removal.
The card's biggest problem is that there's limited room for 6+CC cards in a deck, and there are a lot of good cards up there. I could perhaps see him pop up in a priest control deck. They have fewer good high end creatures than druids, and 7 life is a lot to get rid of versus priest.