Here's a super useful creature that can make Dragons, but most of the time, you'll probably just use him to swing.for 2 or maybe 3 or 4 damage in the air. 6 mana is a big investment in a red deck, although a RG Devotion deck dedicated to Dragons may be able to pull it off.
In Commander, Zirilian of the Claw decks may find room for the Whisperer, as well as some of the other Dragon Commanders, especially the Red/Green/X Legendary Dragons. Just to have a creature that can make Dragons, while providing some early damage, is useful for those decks, as Dragon decks typically take some time to get rolling.
The Whisperer is a nice complement to Dragonmaster Outcast, a mythic rare from Worldwake that’s already popular in Commander. The Outcast creates a 5/5 flying Dragon at the beginning of your upkeep if you control 6 or more lands, and it’s only a 1-drop (R) creature. The Whisperer is better than Kargan Dragonlord, though, another two-drop creature mythic rare (from Rise of the Eldrazi) that requires quite a mana investment to level up into a trampling flyer. Truthfully, the Whisperer has more in common with the Dragonlord, except that it actually creates Dragons, whereas the Dragonlord mimics becoming one.
While the Whisperer may see some play in Standard, it's one of those flavorful cards that may take time to see how it fits into the current metagame. Despite the high raw power of the card, its more like its inferior cousin Kargan Dragonlord than a Dragonmaster Outcast. It may just prove to be too slow for competitive play. In any case, it will be a fun card in Limited, Commander, and casual play.