While the ability seems a bit overcosted at five mana, Azure Mage was pretty good at drawing cards at 3U, only one mana less. The Feeder is basically an upgraded Azure Mage and as the ability is repeatable and able to be played at instant speed, control decks are often leaving up plenty of mana for counter magic as it is. A free card that also denies your opponent one of their cards seems worth that price.
While I think this is definitely Constructed-playable, and most certainly good in Limited where the Ingest and extra ability to exile are even more relevant, I think a lot of Blue/Black Commanders will like this guy. 5 mana for draw a card and exile a card from each opponent’s library is perfectly fine in that often grindy format. Circu, Dimir Lobotomist, Mirko Vosk, Mind Drinker, and Phenax, God of Deception are a few Commanders that would probably welcome the Feeder into their forces. These sorts of blue/black Commanders often can produce tons of black mana, so only requiring a single blue mana for each activation of that ability is a big deal.
How much play the Feeder sees will depend on just how much you can do with your opponents’ exiled cards in the long run. Oblivion Sower will help you grab tons of lands, certainly, but what other crazy effects are on the horizon? If Ingest becomes a viable Constructed strategy, expect to see playsets of this guy going like crazy.
(9/9/15 - English name confirmed to be Fathom Feeder)