Nomenclature varies. Hearthstone is new so things don't have the most standard of names yet.
There's two families of decks that use Flame Imp, the "aggro" "face warlock" variants are characterized by Leper Gnome, Arcane Golem, Elvish Archers, Wolf Riders, Abusive Sarges, Hellfires, Argent Commanders, Power Overwhelmings, owls, and of course, Leeroy Jenkins. Although Doomguard has charge, I believe these lists will actually exclude Doomguard because discarding direct damage cards like Sarge is too costly. In fact, they'll occasionally throw a loot hoarder in.
Standard zoo lists will have less of those cards I mentioned, and they'll also have Shieldbearers, Doomguards, Blood Knights and Shattered Sun Clerics that the face warlocks are less likely to run. These decks intend to gain control of the board turn one and keep control of the board until the game ends. The aggro variants want a temporary control of the board, if any control at all, and are happy to do the last 10+ points of damage by zipping chargers and direct damage past tauntless minions.
Standard zoo does not want Leeroy. Sometimes you might put Leeroy in standard zoo just for surprise factor, but in a vacuum, you don't put him in standard zoo. Since Leeroy does not help maintain control of the board in turns 1-6 he will never be played, and inevitably Doomguard or Soulfire will pitch him away before standard zoo's 1/5 shieldbearers have poked the enemy down to six health. It's better to run a 1 drop in Leeroy's place that can jump out of hand before Doomguard can pitch him (or her), or another board control card.
Standard zoo has 2 Defenders of Argus at rare, 2 Young Priestesses at rare, and 2 Doomguards at epic. So it's a pretty cheap deck, and it's the only proven legendless deck afaik.