Look guys.. this whole 'it nets me 2 energy' argument is pretty weak. Like, you spent 6 mana.. dodged a removal spell, probably got smacked in the face, then spent 6 mana again. Let's be fair.. you spent 6 mana to basically counter a (low cost) removal spell, and gain two energy. That's not a fantastic rate or anything. The only scenario where I see blowing 6 mana per turn on this guy is where you have 9-12 mana on the field and can do other things. If it's taking your whole turn.. you're probably getting your ass kicked.
This is exactly why it is a finisher for Control decks and not a high end beater for Midrange decks Beast.
Control decks usually run a very limited amount of finishers, so the ones they do run generally have to either turn the game instantly as soon as they hit the field, or they have to have some sort of way to protect or recur themselves. Remember that in a Control shell, they preferably aren't going to be dropping their finishers until they have achieved a soft lock, or at the very least stabilized themselves.
Playing Whale for example, then instantly unsummoning it to dodge removal isn't that terrible of a move when you consider that the deck in question is probably only running a minimal amount of finishers (or threats in general), so being able to keep the few that you have alive often makes a big difference.
Keep in mind also that we are talking a Control shell here. With some smart play, there shouldn't be too many times where you unsummon your whale to dodge removal, only to take a bunch of damage from unblocked creatures. Remember that being a Control deck, most, if not all, of the turns leading up to playing Whale are likely going to be spent casting removal, counterspells, mass removal, or draw spells. As such there is a decent chance that when you finally do drop the whale you are doing so onto a board that is at least (relatively) clear.
Control decks are also more likely to play their threats off curve, specifically because they usually run so few of them. Why do you think so many Control players have been howling over
Negate? Waiting until you have 2-3 extra mana on the table to be able to cast Negate (or use another counterspell) on the same turn you cast your finisher is an EXTREMELY common tactic among control players used to keep their finishers safe from removal and counterspells. So it doesn't seem too unlikely to be able to drop Whale, unsummon it to dodge removal, and still have a few mana up for a counterspell or removal should your opponent be able to muster up an attack that turn.